A fresh crackdown on Islamist extremism risks backfiring by fuelling anti-Muslim prejudice and driving hardliners underground, the Government was warned last night.

A group that monitors attacks on Muslims said it was preparing for an upsurge of violence as a result of the moves being announced today by David Cameron.

Under the Prime Minister’s proposals, Islamist radicals face being expelled from mosques, Muslim community groups and universities in a fight-back against fundamentalism.

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The courts would be given new civil powers – similar to Asbos – to ban suspected extremists from preaching or indoctrinating others.

At the same time internet companies have been asked to block terrorist material from overseas being accessed in this country.

The measures were proposed by the Prime Minister’s extremism task force – which included ministers, community groups, the police and the security services – set up after the killing of Lee Rigby.

Last night Fiyaz Mughal, the director of Tell Mama, which records anti-Muslim incidents, said he feared Mr Cameron’s announcements would reinforce negative perceptions of Muslims.

Mr Mughal said he had asked extra staff to be on standby because of an anticipated surge in hate attacks. He added that the new rules should cover all forms of extremism, including the activities of the far right.

“There has to be parity and not a feeling that Muslims are being singled out,” he said.

Chris Allen, an expert on Islamophobia at Birmingham University, said: “The more the lens is turned on the Muslim community, the more society begins to think, ‘There’s no smoke without fire’.”

Isabella Sankey, the director of policy at Liberty, said it was important to confront “ugly ideologies across the spectrum”. But she added: “Driving those who despise diversity further underground does nothing to expose their beliefs and only acts as another recruitment tool. You cannot protect our democracy by shutting down the very freedoms that sustain it.”

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Speaking in China, Mr Cameron defended the proposals. “In light of the dreadful events in Woolwich, I thought it was very important to have a proper look through all of the UK’s institutions to make sure we really are doing everything we can to drive out radicalisation,” he said.

“This is not just about violent extremism, this is about extremism that leads to radicalisation and particularly Islamist extremism.”

Mr Cameron said there were “just too many people” who had been radicalised at Islamic centres or who had been in contact with extremist preachers, who had “not been sufficiently challenged”.

“I want to make sure in our country that we do this effectively. But we need to go further than that and realise that some institutions have wanted to get rid of radicalisers but have not had the means to do so – so we want to help Islamic centres and mosques to expel the extremists.”

The report includes a definition of Islamist extremism as a distinct ideology which, it says, should not be confused with traditional religious practice. It describes it as an ideology which is based on a “distorted interpretation of Islam, which betrays Islam’s peaceful principles”.

The report says Islamist extremists seek to impose a global Islamic state governed by their interpretation of sharia as state law, rejecting liberal values such as democracy, the rule of law and equality. Their ideology also includes the uncompromising belief that people cannot be Muslim and British.