Twenty-five schools in Birmingham are now under investigation following 200 complaints received by the council in relation to allegations of Islamist "takeovers", according to the leader of the city council.

Sir Albert Bore detailed the investigations as he announced the appointment of a new chief adviser to deal exclusively with the fallout from Operation Trojan Horse – a dossier claiming to reveal a plot to "overthrow" teachers and governors in secular state schools in the city and run them on strict Islamic principles.

Birmingham MP Khalid Mahmood said 20 headteachers in his Perry Barr constituency alone – "virtually all Muslim heads" – had raised concerns about potential plots.

Despite fears the Trojan Horse document was a hoax, Mahmood said he'd been made aware of similar allegations over the past 12 years and that he was confident there had been concerted attempts to take over Birmingham schools by Islamic fundamentalists from the Wahabi or Salafi sect.

Allegations have also emerged involving schools outside Birmingham, including the Laisterdyke Business and Enterprise College in Bradford. It emerged on Monday that Laisterdyke's entire governing body has been sacked by Bradford council amid concerns over poor performance and a "dysfunctional" relationship between governors, including two city councillors, and management.

Laisterdyke's female, white headteacher is thought to have complained of coming under pressure to quit by a few influential, hardline Muslim governors who firmly deny trying to oust her.

In a press briefing in Birmingham on Monday, Bore said: "There are certainly issues in Bradford which have similarities with the issues being spoken about in Birmingham."

Bore also announced that Ian Kershaw, a former headteacher with experience of leading independent inquiries, has been given a six-month contract by the council to "analyse further all Trojan Horse material to enable us to see the whole picture", according to a statement put out by the council on Monday.

He is currently managing director of Northern Education, a company working in partnership with schools, local authorities and other agencies.

Kershaw will co-ordinate with the existing Trojan Horse operational group, which is made up of officers from Birmingham city council, West Midlands police, the National Association of Headteachers (NAHT) and the school inspection authority Ofsted. "[The group] will continue to meet regularly, as it has since the Trojan Horse document was first received. Its role will continue to be the co-ordination and oversight of the process of investigation and intelligence sharing," said the council spokeswoman.

A new review group with a wider membership across education, police, politics and faith will also be established this month to oversee Kershaw's work and the operational group, the council said. The review group will be chaired by Stephen Rimmer, Home Office director general, and will include MPs, representatives from the national bodies for school governors and heads, and councillors.

Kershaw will report back to the city council's own jointly convened social cohesion and education scrutiny committees in May.

In addition, the council has asked Birmingham's Young People's Parliament to carry out a piece of work during the summer term to address two particular questions: "What does a good, inclusive education in Birmingham look like?" and "What does a safe and resilient citizen of the future look like?"

By summer, the city council will publish a report setting out its recommendations to be implemented locally and nationally by the DfE and others.

At the weekend, it emerged that the education secretary, Michael Gove, had personally sent Ofsted in to inspect 15 Birmingham schools in recent weeks, after the allegations first broke.

Concerns over how some of the city's 430 schools were being run first emerged when an anonymous letter known as Operation Trojan Horse was leaked to councils and teaching unions, claiming that a small but radical group of Muslims were pursuing their own agenda in the classrooms, with non-compliant headteachers and governors forced out.

The document, which is unsigned and undated, claimed to have caused "a great amount of organised disruption" in the city, crediting the plan with forcing a change of leadership at four schools.

Since the letter came to light, anonymous whistleblowers, including former staff, have come forward, making claims that boys and girls were segregated in classrooms and assemblies, sex education was banned, and non-Muslim staff were bullied. In one case it was alleged that the teachings of a firebrand al Qaida-linked Muslim preacher were praised to pupils.

In Bradford, one of the sacked governors from Laisterdyke said on Monday that the governing body had been unfairly removed. Faisal Khan, an independent councillor (formerly with George Galloway's Respect party), said the head, Jen McIntosh, had refused to take instructions from the governing body and had colluded with the council to get them all sacked after they refused to "rubber stamp" an internal appointment.

Khan said that latterly all but one of the governors at the school were Muslim but denied being part of any Islamist plot. Such allegations, he said, aimed to cause "mischief" and were invented by those who "believe Muslims should not serve as governors".

He said Operation Trojan Horse was an invention by anonymous voices looking to drown out legitimate concerns raised by Muslim governors trying to push standards up at schools.

"I've spent the last eight years encouraging members of the community to be part of the 'big society', as David Cameron calls it, and become governors. How can I continue doing that given this shoddy behaviour, when Muslim governors are being treated so unfairly?"Mohammed Shafiq, Chief Executive of the Ramadhan Foundation urged calm while allowing authorities to continue their investigations. "The allegations of alleged extremist takeover of schools in Birmingham are very serious however there is a wider concern that this is a witch-hunt against the Muslim community." he said.

"I am very clear that if these allegations are proven then all stakeholders will need to work together to ensure that it does not happen again but equally this could be a hoax dreamt up without any evidence. It is important that Muslim parents and the wider community who take an interest in schools and education where they represent their children's interests are not seen as extremist when ensuring their religious needs are being met; this is something that should be encouraged and celebrated. Sadly the events of the past few months will lead to parents being reluctant of coming forward to support schools and it is the children and schools that will suffer."