Attempts to incorporate stringent Islamic practices into UK schools may have proliferated from Birmingham to other cities, the London Times reports. School governors may have violated employment procedures by hiring staff based on their Islamic adherence as opposed to their skill sets, said Russell Hobby, general secretary of the National Association of Head Teachers (NAHT).

This marks the first time that school leaders have acknowledged that claims related to Islamist influences permeating in Birmingham schools may be justified. UK investigators are conducting inspections at 21 Birmingham schools, and the city council is examining complaints regarding about 30 schools.

UK Prime Minister David Cameron has become personally involved in combatting alleged Islamist infiltration into UK schools, the Times reports.

"I am hugely concerned about the allegations…I don't want to see Islamist entryism into our schools. That is a very worrying development," said Cameron.

Hobby believes that the "Trojan horse" plot by extremist Muslims to dominate schools in Birmingham is connected to other "large cities," but refused to name any.

"A tight network of religious leaders of the Islamic faith has made a concerted effort to get involved in the running of schools and to strengthen the power of governing bodies to have a dominant influence in shaping the character of local schools," said Hobby.

The allegations include some governors forcing schools to incorporate strict Islamic practices. Some of the concerns involve denying children, particularly girls, sex education, or music and arts lessons, if it is perceived to contradict Islamic teachings. In the past six months, five non-Muslim head teachers resigned.