Ofsted is to hold an independent investigation into fresh claims that Norfolk academies had “improperly” been tipped off ahead of their inspections.

Last month, an internal report by the watchdog concluded there was “no evidence” that the Ormiston Victory, Thetford or Great Yarmouth academies had been warned “to give them an unfair advantage”.

However it revealed that Dame Rachel de Souza, chief executive of the Inspiration Trust academy chain which runs the Thetford and Great Yarmouth schools, had inadvertently been informed about an impending inspection during her training as an additional inspector. The date of the inspection was subsequently changed.

Newspaper reports last weekend said that new emails had emerged, not available at the time of the original investigation, which suggested that Dame de Souza had been made aware of specific plans for inspection and advised staff to prepare accordingly.

On Monday, a statement released by Ofsted said they did not believe the claims added “anything of substance” to the internal report carried out by Sir Robin Bosher.

But today chief inspector Sir Michael Wilshaw announced that he is to “appoint an independent figure to review and assure the internal investigation carried out by Ofsted into alleged inspection irregularities in three Norfolk schools”.

In today’s announcement, Sir Michael said: “The ongoing claims that have been made about certain schools in Norfolk being given advance notice of Ofsted inspections are very serious…

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

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Ofsted must scrap ‘quality of teaching’ from inspections - July 2014

Ofsted to drop grades for teachers’ individual lessons in new trial - June 2014

Ofsted should no longer judge quality of teaching, says former Gove aide - May 2014