LONDON (REUTERS) - Schools in Birmingham were exposed to a "sustained and coordinated" effort to impose a hardline Muslim agenda on pupils, a government investigation led by London's former counter-terrorism chief said on Tuesday.

The report was commissioned to look into an alleged campaign by Muslim extremists, dubbed "Operation Trojan Horse", to force some schools with large numbers of Muslim pupils to adopt a more Islamic culture by installing governors and teaching staff who would support a conservative Islamic religious agenda.

"There has been co-ordinated, deliberate and sustained action, carried out by a number of associated individuals, to introduce an intolerant and aggressive Islamic ethos into a few schools in Birmingham," said the report by Peter Clarke, former head of London Metropolitan Police's Counter Terrorism Command.

The Trojan Horse allegations were first made in an anonymous letter to Birmingham Council. The letter's veracity has since been disputed, but the government has taken its claim seriously and launched a series of investigations.

A report by schools inspectors last month found a culture of"fear and intimidation" existed in some Birmingham schools and said there were cases where schools had shirked their responsibilities to protect children against religious extremism.

That report was criticised by the Muslim Council of Britain, who said it could be viewed as a witch hunt.