Ofsted has published 21 reports of inspections into schools linked to the alleged “Trojan Horse” plot, with five of the schools placed in special measures.

These include three schools run by the Park View Educational Trust - Park View, Golden Hillock and Nansen - along with Oldknow Academy and Saltley School, which have also been rated inadequate.

Ofsted has accused the schools of failing to take sufficient action to prevent students being exposed to Islamic extremism. The accusations, however, have been strongly rejected by the schools concerned.

An advice note from chief inspector Sir Michel Wilshaw sent to education secretary Michael Gove said that a “culture of fear and intimidation” has developed in some of the schools.

Of the other 16 schools which were subjected to monitoring inspections, all were found to meet the mandatory requirements for safeguarding.

One of the schools, Alston Primary, has already been placed in special measures. Leadership and management was rated as requiring improvement in 11 of the schools, good in one and outstanding in three others.

In his letter to Mr Gove, Sir Michael said that governors at some schools had “exerted inappropriate influence on policy and the day-to-day running of several schools”, adding that Birmingham City Council had “failed to support a number of schools in their efforts to keep pupils safe from the potential risks of radicalisation and extremism”.

The report on Park View, which was rated outstanding by the watchdog just two years ago, said its “work to raise students’ awareness of the risks of extremism is inadequate”.

The academy was criticised for failing to vet external speakers properly, particularly with regard to “Islamic-themed assemblies”, and inspectors also claimed the school had “not taught sex and relationships education effectively”.

There were also “few opportunities for students to learn about different types of beliefs and cultures in the older year groups”, while student were “prepared properly for life in a diverse and multicultural society”, the report added.

Saltley was rated inadequate in every category. “Many of the governors refuse to accept that the school is in a state of crisis”, the report said.

While Oldknow Academy was rated outstanding for achievement of pupils and quality of teaching, it was rated inadequate for behaviour and safety of pupils and leadership and management.

“Governors do not meet their statutory responsibilities to safeguard pupils because they have not taken steps to protect them from the risks of radicalisation and extremism”, the report said. It added that “a small group of governors” was “making significant changes to the ethos and culture of the academy without full consultation ... and ... endeavouring to promote a particular and narrow faith-based ideology in what is a maintained and non-faith academy”.

It added that a madrasa, a school for teaching Islamic theology, had been established in the school and “paid for from the academy’s budget”, which had also been used to subsidise a trip to Saudi Arabia for only Muslim staff and pupils.

The leadership team at Nansen primary, Ofsted said, “do not sufficiently develop pupils’ understanding of the different customs, traditions or religions that exist in Britain. This does not prepare pupils adequately for life in modern Britain.”

Leaders of the schools concerned, however, have been quick to condemn the findings, with Park View announcing that it planned to mount a legal challenge to the judgements.

Lee Donaghy, assistant principal of Park View School, said its staff “reject” the report’s findings.

“It is simply not true that the school does not do enough to protect our pupils from the risks of extremism,” he said. “Every day, my colleagues and I work hard to ensure our pupils are disciplined, understand and respect difference and most of all achieve well, and in the process gain a full understanding of their religion - the surest guards against extremism of any kind.”

A statement issued by Saltley School said inspectors “found not the slightest shred of evidence” of influence by Islamic extremists. “Parents and the wider community may be wholly confident that students here are safe and well looked after,” it added.