The educational trust at the centre of the "Trojan horse" controversy says the "knee-jerk" actions of politicians has put the future of students in jeopardy, as it confirmed that its three Birmingham schools have been put into special measures by Ofsted.

Park View Educational Trust claimed Ofsted inspectors had gone into schools looking for extremism and religious segregation.

David Hughes, vice-chairman of the trust, launched a passionate defence of the school's record, saying it was helping children from one of the poorest neighbourhoods in the UK to aspire to a decent future. He claimed the investigations were undermining community cohesion and said the trust would be legally challenging the Ofsted findings.

At the start of his statement at Park View school in Washwood Heath, north Birmingham, Hughes emphasised that he was proud of the school – and of his own Anglican religion.

He confirmed that Park View and its sister schools, Golden Hillock and Nansen primary, had been deemed inadequate by Ofsted and were being put into special measures.

"We wholeheartedly dispute the validity of these gradings. Park View, Golden Hillock and Nansen are categorically not failing schools.

"The Ofsted inspections were ordered in a climate of suspicion created by the hoax 'Trojan' letter and the anonymous, unproven allegations about our schools in the media.

"Ofsted inspectors came to our schools looking for extremism, for segregation, for proof that our children were having religion forced upon them as part of a Muslim plot. The Ofsted reports found absolutely no evidence of this as this is categorically not what is happening.

"Our schools do not tolerate or promote extremism of any kind. We have made a major commitment to raising students' awareness of extremism. People who know and worked with our schools are appalled at the way we have been misrepresented."

Hughes said the inspections had put at risk the work the schools were doing to improve community cohesion.

"They have put Muslim children from these communities at substantial risk of not being accepted as equal, legitimate and valued members of British society and they have allowed suspicion to be cast on the aspirations of their parents and anyone else who believes that these children deserve the same excellent standards of education as any other child. We will be challenging all these reports through the appropriate legal channels."

Lee Donaghy, assistant principal at Park View school, 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 … This is a normal state school, like thousands of others across Britain – 98% of our pupils just happen to be Muslims. British Muslims.

"We have nothing to hide. Talk to the parents, talk to our former pupils. They will tell you this is an outstanding school, with outstanding results, where pupils are taught right from wrong. They will tell you there is no segregation or extremism."

The trust's statement came before the release of a tranche of reports by the school inspectorate, Ofsted, into Birmingham schools, and a statement in the Commons by the education secretary, Michael Gove, that is expected to propose a raft of measures to end covert religious education.

Earlier, David Blunkett, the former education secretary, said the government's excessive relaxation of oversight over schools had led to a vacuum that had allowed forces opposed to British liberal values to flourish in them.

Blunkett pointed to the removal of the national curriculum from academies and the lack of regional oversight of schools, leaving too much responsibility in the hands of the Department for Education.

He said there was a muddle in the heart of government about whether schools should be left alone in an atomised, fractured system.

Blunkett and the shadow education secretary, Tristam Hunt, argue that the crisis has shown the wisdom of their plan for greater regional oversight of schools.

He called for a cross-party review of allegations of Islamic extremists infiltrating schools and said the problem was much bigger and more important than Gove's ideology.

"This is about the nature of the future of our society and our society does need an open, liberal curriculum that embraces all faiths and no faiths, that teaches children to think for themselves, to examine the evidence, to be able to come to decisions rather than having any ideology, any politics, any faith pushed down their throat, and that is the nature of the type of education we want," Blunkett said.

"My main concern at the moment is that people seemed to have missed the point that we have a national curriculum, although we no longer have a curriculum authority because it was abolished back in 2011, and we have a national curriculum that doesn't apply to all schools, it doesn't apply to Park View academy trust because they are academy schools and they are outside the curriculum.

"So we need to get back to first principles: firstly, should we have a local level of oversight that works; secondly, should we distinguish clearly between what threatens our liberty, our life, and that which threatens our small 'l' liberal society, which was built into the curriculum; and thirdly, whose responsibility is it to do something about it?"

He said at present England had an "Education Funding Agency whose job isn't about funding but about going in to investigate a trust; you can't have an inspectorate that are called in not to deal with the quality of education in schools, but with an ideological question".

Blunkett said it would be dangerous if Muslims felt under attack, but more needed to be done to "make sure the madrassas outside school night after night and at weekends don't preach something, don't inculcate into the young minds things that we find unacceptable".

There are tensions in the Birmingham Labour party, with some senior politicians who have been governors at some of the schools under question deeply resenting suggestions that they have allowed extremism to foster.

Figures such as Liam Byrne, the shadow higher education minister and the MP for Birmingham Hodge Hill, are supporting demands in the community for more explicitly faith-led schools, which they say could minimise the likelihood that communities will subvert secular schools into de facto religious schools.

The plan for snap inspections, due to be outlined on Monday, was supported by Khalid Mahmood, the MP for Birmingham Perry Barr and the Labour politician most active in warning about potential extremism.

He said: "If schools are doing what they should be doing in the first instance, there shouldn't be any difficulty with that and I think the whole idea is to get a true reflection of what the schools are doing.

"By giving these traditional notices, people can adjust certain things and do things that they perhaps wouldn't do normally – and certainly in these schools, that's the case.

"When I've spoken to parents and I've spoken to some of the governors who have been ousted and some of the teachers existing in some of these schools, that's exactly what they've said, that they were able to change some of these things in order to show that they were actually operating in a different way to what they were."