25 British schools are being investigated in connection with an alleged plot by conservative Muslims to force out headteachers and governors.

A new chief advisor is now being appointed by Birmingham City Council to handle the at least 200 complaints received in relation to 'Operation Trojan Horse' after an unsigned, undated document was sent to the Council and teaching unions last year.

It apparently set out a blueprint for seizing control of the governing bodies of schools, and forcing out those who do not agree. It claimed to have forced a change of leadership at four schools.

Whistleblowers - including former staff - have made a number of allegations against schools in Birmingham since the accusations came to light, including one claim the teachings of an al-Qaeda-linked preacher were praised in front of pupils.

Other complaints include the alleged segregation of boys and girls in lessons and assemblies, a ban on sex education and bullying of non-Muslim staff.

"Similar" issues in other cities

The British Deputy Prime Minister Nick Clegg said he was "very, very concerned about allegations that taxpayer-funded schools have become vehicles of particular ideologies".

"I have always supported faith schools but the best faith schools use their religious identity as engines of integration rather than silos of segregation," he added.

The Council's investigation, running alongside a separate inquiry by the British Department for Education, is due to initially report back in May.

At a briefing, councillors said the 25 schools being investigated in Birmingham included primary, secondary, community schools and academies. 15 of the schools have so far been inspected by Ofsted - the official UK body for inspecting schools.

Birmingham City Council also confirmed that it was in contact with authorities in Bradford and Manchester who had been experiencing "similar" issues.

A British Department for Education spokesperson said "The allegations made in relation to some schools in Birmingham are very serious and we are investigating all evidence put to us in conjunction with Ofsted, Birmingham City Council and the police. It is absolutely vital these investigations are carried out impartially, without pre-judgment. It would be inappropriate to comment further at this stage".