LONDON (REUTERS) - Britain's top school inspector said on Monday that an investigation into an alleged plot by extremist Muslims to take over the running of some schools in the city of Birmingham had found that a culture of "fear and intimidation" existed.

In March, an official investigation was sparked by an anonymous, unverified letter which claimed there was a plot to force some state schools in Birmingham with majority-Muslim pupils to adopt a more Islamic culture by installing school governors and teaching staff who would support a conservative Islamic religious agenda.

"Some of our findings are deeply worrying, and in some ways quite shocking," said Michael Wilshaw, head of the Ofsted schools inspectorate. "In the most serious cases, a culture of fear and intimidation has taken grip."

He added that some schools had not taken their responsibility to protect children against religious extremism seriously enough, and that in one case a guest speaker with known extremist views had been invited to speak to pupils.

David Hughes, Vice-Chairman of Park View Educational Trust which runs some of the schools implicated, rejected the conclusions of the report, saying the Ofsted inspections had been carried out in a climate of suspicion. He said the schools did not tolerate or promote extremism of any kind.