British Prime Minister David Cameron promises a "robust response" to the "culture of fear and intimidation" that British investigators found at five state schools in Birmingham, England, where Islamic extremists allegedly plotted to subvert and run them according to rigid Islamic norms.

A report released Monday by the U.K.'s Office for Standards in Education, Children's Services and Skills (Ofsted) found evidence that certain governors of the affected schools had tried to "impose a narrow faith-based ideology."

In some cases, staff and headteachers said that they had felt "intimidated," "undermined" or bullied by the governors into making changes they opposed. Some headteachers, including those with records of improving standards were either marginalized or forced out of their jobs.

"Some teachers reported that they were treated unfairly because of their gender or religious beliefs," said Ofsted director Sir Michael Wilshaw.

One primary school's governors opposed mixed-gender swimming lessons despite the headteacher's commitment to having them. Wilshaw also noted that the governors excessively micromanaged the schools' day-to-day operations.

One school hosted a guest speaker who previously prayed for victory for Muslims in Afghanistan, in addition to "victory to all the Mujahideen all over the world. Oh Allah, prepare us for the jihad."

The report was prompted by an alleged plot for Islamists to take control of public schools that surfaced in March. The five-step "Operation Trojan Horse" plot was detailed in a letter suspected by some of being a hoax. It focused on schools with large Muslim populations to have "hardline" parents turn against the teachers and school leadership. Those staffers would be replaced with people who would then run the schools according to a radical interpretation of Islam.

News of the letter sparked cries of "Islamophobia" and "fabrication" from Tahir Alam, director of the Park View Educational Trust that runs the schools, who had been implicated as a plotter.

A report by the Education Funding Agency (EFA) – the agency that oversees academies in the U.K. – found that the schools hastily replaced a literacy lesson at one school with a lesson about Christianity when they knew inspectors were coming.

EFA also found that Park View School, Golden Hillock School and the Nansen Primary School were teaching curriculum from a "conservative Islamic perspective" in violation of British law, which requires non-faith schools to be nonsectarian.

Consequently, Ofsted informed Cameron that it will conduct unannounced random inspections, and provide him and the U.K.'s education minister with reports on the situation in Birmingham until the situation has been fully resolved.

David Hughes, a governor with the Park View Educational Trust, dismissed the Ofsted report, saying that his schools had been "grossly misrepresented" as having been "infiltrated by extremists."

The Trojan Horse plot was an unfounded smear, Hughes said, and that the investigations were are the result of an anti-Islamic agenda.