Ofsted will still inspect Sunday schools and other church groups under anti-terrorism laws, it was claimed on Monday, despite government assurances they had moderated plans.

Measures in counter-extremism legislation had vowed to force "out-of-school settings" that taught children for "more than six to eight hours a week" to register with the government and face inspections if concerns were raised. Although the law aimed to target a small number of Muslim madrassas, Church leaders were concerned some Christian youth groups could cross the six-hour threshold.

On Sunday it emerged the government would drop the requirement for Church youth groups to register.

But Church could still face inspections by the school regulatory body Ofsted, one MP told Christian Today.

Fiona Bruce, MP for Congleton and a Christian who has opposed the plans, warned the government's assurances should be "met with caution until it presents its revised plans". She added "preferably, the Government should scrap its original proposals altogether".

One Whitehall source told the Sunday Times that although enforced registration of churches had been dropped because it was "too draconian", it still means Ofsted can inspect "if there is reasonable cause".

It is not yet clear what "reasonable cause" consists of and a number of Christian leaders are concerned that churches could be subject to vexatious complaints. There is not yet any indication whether inspections will be carried out on the basis of alleged criminal activity or simply on the basis of teaching contrary to 'British values'.

Several Tory MPs, including Bruce, have warned the powers could be used by opponents to target Christian groups that teach marriage is between a man and a woman.

"We have yet to see their alternative proposals, but any counter-extremism measures must be effectively and specifically targeted only on those who threaten the peace and incite violent extremism," said Bruce.

"They must not be a pretext for lazy catch-all legislation or to be used or abused to stifle the freedom of speech and expression of those who merely have minority views on social, ethical or religious issues. 

"This means not only that Sunday schools should not be affected – it means the same for any range of places where ideas and beliefs are discussed. It is not for the Government to draw up a list of approved beliefs on social, ethical or religious issues. The Government's duty is to restrain and penalise violent conduct."