The inspectorate said the development followed “the emergence … of a number of new emails” that were not available during an earlier investigation led by an Ofsted director, which found no evidence that the schools had received such an advantage.

Announcing the new investigation this afternoon, HM Chief Inspector Sir Michael Wilshaw said that an “independent reviewer” would be appointed to look at both the new evidence, and evidence considered in the earlier review.

The allegations relate to three schools in Norfolk with links to Dame Rachel de Souza, now chief executive of the Inspiration Trust academy chain.

After claims that the schools received advanced notice of their inspections were published by the Observer in August, Ofsted’s director of quality and training Sir Robin Bosher investigated the claims. His report, published last month, concluded there was no evidence to substantiate claims that the schools had received an unfair advantage.

Further allegations were published by the newspaper on Sunday, however, based on internal emails involving Dame Rachel.

The allegations have been strongly denied by Dame Rachel, and earlier this week the chairman of Inspiration Trust, which runs two of the schools concerned, said that he did not think there should a further investigation of the claims.

Speaking to Academies Week on Monday, Inspiration Trust chairman Theodore Agnew said: “I certainly don’t think [an independent investigation] would be worthwhile, it would be a huge waste of time and money. It would be distracting for everyone involved.

“We have taken over four failing schools in two years. Every time you are spending time on these kinds of things, it just takes time away from educating the kids.”

At the time of writing, the trust has not commented on news that a new investigation is to be carried out.

In a statement announcing the development, Sir Michael Wilshaw, Ofsted Chief Inspector, said: “The ongoing claims that have been made about certain schools in Norfolk being given advance notice of Ofsted inspections are very serious.

“It is vital that the public has absolute confidence in the integrity of the inspection process. That is why I immediately asked Sir Robin Bosher to examine these allegations when they first surfaced in August.

“Sir Robin conducted a thorough investigation, which included 39 interviews with relevant parties and visits to the three academies in question. But I made a public commitment that should any additional evidence come to light, I would have no hesitation in bringing in someone from outside Ofsted to examine this.

“For the avoidance of any doubt, I will be asking this independent reviewer to examine all the evidence originally considered by Sir Robin and to establish whether his findings and recommendations still stand in the light of the new email evidence that has now emerged.”

The inspectorate said that the appointment of the independent reviewer would be confirmed in the next few days.

The news follows a call at the weekend from Shadow Education Minister Kevin Brennan for a “transparent and forensic investigation” into the claims made by the Observer.

UPDATE, 17:25, 24 October 2014:

A response to the announcement from Ofsted has now been issued by the Inspiration Trust.

Theodore Agnew, chairman of the trust, said: “We welcome this new review as an opportunity to lay to rest once and for all these serious allegations, which we believe to be false. We are confident that this new and independent review will confirm the conclusions of the previous in-depth Ofsted investigation, which found no evidence that anybody had been tipped off about the dates of Ofsted inspections.

“In the situations under consideration, there was a narrow window in which Ofsted could arrive and the staff were simply in a high state of eagerness and anticipation. They had no inside knowledge.”

Dame Rachel de Souza, chief executive of the trust, said: “The independence of Ofsted is paramount in our educational system and I look forward to the independent reviewer getting to the bottom of these false allegations.

“I am deeply committed, as is the entire Inspiration Trust team, to educational progress in Norfolk and we are determined not to let these false and upsetting allegations distract us from our work in giving children the best education possible.”

Under the Data Protection Act, teachers are allowed to request lesson observation notes written by Ofsted during their inspection.

One teacher, writing on his blog earlier in the week, outlined how he went through the process to access observation notes on his lesson from an Ofsted inspection earlier this year. However, one he received the information, the inspectorate said he must not share or publish it due to the rules of ‘Crown Copyright’.

Speaking with Academies Week, Ofsted said it was unable to make a decision on whether the copyright could be waived – as it rests with the Controller of Her Majesty’s Stationery Office – and would not comment on individual cases.

Tim Turner, of 2040 Training and who specialises in data protection law, said the quoting of these rules usually prevents the publishing of material in its original form, but discussing the information could be possible.

He said: “Technically, yes, the Crown does own the copyright but I have never heard of a case in this context.

“It is a defensive move, precisely to inhibit people from sharing information. But there is no public interest in preventing the sharing of this information, and it would be of no loss to Ofsted is this was published. Sharing is usually only challenged if it is used to make money out of the information.”

Ofsted has also recently removed a form on its website which previously enabled teachers easily submit subject access requests – a process enabling individuals to find out what information an organisation holds about them.

Explaining why the request forms were removed, an Ofsted spokesman said: “There was a brief period when this was available but it is not there anymore. It is to do with the work Mike Cladingbowl has been doing to show we don’t grade lessons.
“It gives the wrong impression if it looks like we are looking at individual teachers.”

The remarks relate to the recent changes in Ofsted’s procedures for grading individual teacher’s lessons during school inspections.

Since the start of September, lessons are no longer individually graded, although inspectors can and do still visit classrooms.

Mr Turner found the removal of the form to be unusual. He added: “It seems very odd to remove something which is helpful.

“The Information Commissioner has encouraged organisations to make information like this much easier to obtain. It does seem like a very unusual step.”

Michael Cladingbowl (pictured) will step down from his post at Ofsted at the end of December and is to become the executive principal of Knutsford Multi-Academy Trust.

The trust is responsible for Knutsford Academy, for pupils in Years 7 to 9, Knutsford College and The Studio at Knutsford which both cater for Years 10 to 13.

Ofsted said he will still work on the future consultation on the new inspection frameworks.

Mr Cladingbowl said: “I’ve thoroughly enjoyed my national role with Ofsted and being able to make a real difference to education standards in England over the last 12 years.

“I will be leaving an organisation whose standing and influence under Sir Michael’s leadership has never been higher.

“But this is the right time for me to be taking on a new challenge.

“I’m very excited to be returning to my roots in Cheshire and being more directly involved in making a difference in schools. Before that, I still have a big job to do steering through Ofsted’s forthcoming consultation on the future of education inspection.”

Her Majesty’s Chief Inspector Sir Michael Wilshaw said: “Mike has made a fantastic contribution to Ofsted for over 12 years. In that time, he has held a number of very senior positions within the organisation, including being one of the pioneering Regional Directors in the North-West.

“A man of ideas, Mike has played a key role in shaping the future operating model for inspection as well as the way the routine inspection of good schools will be organised from September 2015.

“He will be much missed but I know how much he is looking forward to using the experience he has gained at Ofsted to lead an important multi-academy trust in the north-west of England to further success.

“Mike will leave Ofsted at the end of December 2014 but will continue to work on the consultation arrangements for the new inspection frameworks. I would like to put on record my deep appreciation for the support he has given me in my time as Chief Inspector.”

The findings came in the inspectorate’s Below the radar: low-level disruption in the country’s classrooms report – which claims that the equivalent of up to 38 days of teaching was lost per year because of low-level disruption in the classroom.

The report said that where previously more than a fifth of schools – 22 per cent – with an overall effectiveness rating of ‘good’ received an ‘outstanding’ rating for behaviour, this had dropped to 15 per cent following the change in guidance.

Schools rated ‘requires improvement’ and ‘inadequate’ were also less likely to receive a behaviour rating equal or above their overall inspection score.

A survey of teachers carried out by the inspectorate found that only around three in ten secondary teachers felt supported by their headteacher in managing poor behaviour.

“Many teachers indicated that senior leaders were not visible or assertive enough in enforcing discipline, school rules or establishing the right ethos,” the report said.

This came despite a survey parents showing that around two-thirds of parents were keen that school leaders ensured that all staff applied a behaviour policy.

The report also provided more detail of the unannounced behaviour inspections which Ofsted has been carrying out.

The inspectorate carried out 28 of these inspections between January and July 2014, targeting schools where be behaviour had been judged to be less than ‘good’ previously, but where the schools had good leadership so “were likely to have sufficient capacity to tackle the identified areas for improvement”

In almost all of the schools, it visited, inspectors still judged behaviour to require improvement, the report said.

Commenting on the findings, Her Majesty’s Chief Inspector, Sir Michael Wilshaw (pictured) said: “Children need to know the rules and teachers need to know they will be supported in enforcing them.

“That’s why Ofsted has tightened the guidance on behaviour for inspection and increased the number of unannounced inspections undertaken as a result of concerns.  In the last year schools serving almost 450,000 pupils have been judged less than good for behaviour. That is far too many.”

Russell Hobby, general secretary of NAHT said: “Ofsted is contradicting itself. Reports from its routine inspections say behaviour is good or outstanding in 83 per cent of all schools. That’s not yet perfect but it shows a massive improvement.”

Mr Hobby said that the “contradictions” arose in part because Ofsted had changed what it was asking for on behaviour.

“It would help if they had been clear about that and given the system time to clear the new hurdles. It is not ‘failure’ when you are asking more of people,” he said.

Mr Hobby also said that the report “appears to be another way for Ofsted to justify no notice inspections”.

The review, carried out by Sir Robin Bosher, Ofsted’s director of quality and training, concluded that there was no evidence that the three schools named in news report – Ormiston Victory Academy, Thetford Academy and Great Yarmouth Primary Academy – had received any prior warning about their inspections.

“The investigation team found no evidence to substantiate the allegations that the three schools in question had improperly received prior notification of the dates of their Ofsted inspections in order to put them at an unfair advantage,” the report said.

Ofsted chief inspector Sir Michael Wilshaw commissioned the investigation in August, after the Observer newspaper carried allegations that the three academies in Norfolk had received prior knowledge of the date on which they would be inspected.

At the time of the investigations, all three schools were overseen by Dame Rachel de Souza (pictured), chief executive of the Inspiration Trust chain.

The report from Sir Robin recommends, however, that Ofsted looks at adopting a more flexible, “risk-based” approach to the timing of certain types of inspection – making the timing of inspections less predictable. The report acknowledges that under the current system, rules on when inspections are carried out sometimes means “the likely window for inspection can sometimes be narrow”.

The report also recommends that Ofsted examines whether processes meant to ensure the confidentiality of inspection dates need to be tightened up.

The investigation found that Dame Rachel, who also worked part-time as a secondary inspector for Ofsted, was mistakenly copied in on an email that gave the date of an inspection at one of the schools concerned – Great Yarmouth Primary Academy. As a result, the date of the inspection was changed, however, the report said.

The inspectorate said that it had conducted a further inspection of Great Yarmouth Primary Academy this week in light of this finding, “in order to maintain public confidence in the integrity of the inspection process”.

HM Inspectors are to visit about 40 schools across the country for two day inspections during a two week period this month.

Schools are currently given half a day’s notice before Ofsted inspections but Chief Inspector Sir Michael Wilshaw has now agreed to look at a system of inspecting all schools without notice.

Sir Michael revealed the plans for unannounced inspections after the Trojan Horse investigation – an alleged plot to infiltrate schools in Birmingham by Islamists.

No notice inspections for all schools were first mooted by the Department for Education in 2012 but it was withdrawn by Ofsted after Sir Michael said teachers objected to the plans.

Today’s announcement widens powers to undertake no notice inspections  if there are concerns about rapidly declining standards, safeguarding and behavioural issues, standards of leadership or governance, or the “breadth and balance” of the curriculum.

Ofsted said many of the schools were already scheduled for visits this term but others will take place in light of concerns being raised.

Sir Michael said: “Parents rightly expect Ofsted inspections to get to the heart of any problems that may exist in a school – whether they are to do with discipline, safeguarding, poor leadership or governance, or a narrow, unbalanced curriculum. That’s why we’ve expanded the criteria for conducting unannounced inspections for the coming year.

“I’m currently giving thought to whether Ofsted should move to more routine no notice inspections as part of our wider education inspection reforms, which we will be consulting on later this year.

Parents rightly expect Ofsted inspections to get to the heart of any problems that may exist in a school

“In the meantime, under our regional structure, inspectors are well placed to use their local knowledge and contacts to identify where these sorts of problems may be taking hold so we can respond swiftly and report publically on what we find.”

Responding to the Ofsted announcement the National Association of Head Teachers (NAHT) general secretary, Russell Hobby, said: “Ofsted already has the power to conduct a no notice inspection where there is risk or concern and this is sufficient.

“Routine no notice inspections demonstrate a profound lack of trust in school leaders.

They will also paralyse the self-improving school system, making it difficult for heads to spend time out of their schools to help improve standards.”

In the same announcement, Ofsted also confirmed they have returned to five Birmingham schools which were placed in special measures during the Trojan Horse investigation.

Sir Michael joined the inspection team at Park View Academy.

Asked about the extent of self-plagiarism during a question and answer session at today’s researched conference, Ofsted schools director Mike Cladingbowl said that the inspectorate had sacked an inspector for plagiarism.

Also speaking at the event, Sean Harford, Ofsted initial teacher education director, confirmed that at least two inspectors had lost their jobs. It had happened “in the past couple of years”, but he could not remember a more precise date.

Asked by Academies Week whether this represented a larger issue, Mr Cladingbowl said: “If it were true that there were inspectors out there who were routinely going from one inspection to the other, cutting and pasting in the way that one of the myths has it, then we would know about it.

“It has happened in the past [and] we’ve taken action. But I’m pretty confident it’s not routine.”

Also talking to Academies Week after the event, Mr Harford said that the pair involved were additional inspectors who had been dismissed by their contractor. He said that Ofsted gave contractors a “very clear steer about quality of work and acceptability”.

“We are all Ofsted, and Ofsted has responsibility for the quality of our inspections. Clearly we discuss things with contractors through the contract management.”

Mike Cladingbowl, Ofsted schools director and Sean Harford, Ofsted initial teacher education director with education blogger Andrew Old

Mr Cladingbowl and Mr Harford were appearing in a discussion with education blogger Andrew Old as part of the researchED programme.

Earlier in the session, the Ofsted directors were asked whether there was now a greater acceptance by Ofsted of personal decisions and approaches taken by teachers.

They confirmed that this was now the case, and that this was one of the areas in which Ofsted wanted to improve dialogue with teachers.

Individual classes not being graded made observations “lower stakes”, one of the directors said – so teachers should not feel that if that had a bad lesson while being observed that that would necessarily have a bearing on the score the rating the school received.

Mr Cladingbowl and Mr Harford were also asked by Academies Week editor Nick Linford about a suggestion in an education select committee hearing this week that some potential school whistleblowers were not coming forward for fear of triggering an Ofsted inspection

Mr Harford said that it was important that teachers had someone they could raise concerns with – and that Ofsted was that body. He said that he could point to examples where this had happened.

Mr Cladingbowl called for teachers to come forward if they had concerns, although a show of hands of about 200 people in the room suggested that very few would.

At the Education Select Committee’s second meeting on Tuesday after the inquiry into the alleged plot by hardline Islamists to take control of schools in Birmingham, Ian Kershaw told MPs he believed headteachers had not come forward.

He was giving evidence alongside Peter Clarke who was appointed by former Secretary of State Michael Gove to head up a separate inquiry.

Committee chairman Graham Stuart said: “You suggested a number of heads didn’t give evidence, and it might seem ironic to ask after four or five different investigations, but did you have the powers you needed to get to the bottom of this? Did we need to hear from more people and get evidence from them to get the real picture?

Mr Kershaw said: “Well I had no powers, people volunteered their evidence, apart from the powers given to me by the local authority to interrogate all of the information they held.

“I think you have got to understand the atmosphere for headteachers. I have been a headteacher for some years and, at that point in time in Birmingham, with the number of Ofsted inspections that had been taking place I believe from the commentaries I have listened to, there were concerns that if I put my head above the parapet I will invite an inspection.

“And the headteachers think ‘I don’t want to go through an inspection process’, so I think there was a fear level about ‘if I say something about concerns about governors in my school, I will be the next school to be inspected’. So there was a bit of that going on, I believe.”

He added it would be “no easy task” for headteachers to have confidence in the authorities – the city council, the Department for Education and Ofsted – to put matters right.