According to police sources, about 200 of these incidents are deemed significant enough to have potential repercussions within communities.

They include mosques being set alight in Birkenhead, Merseyside, Telford, Shropshire and Leeds.

“We have definitely seen a spike, but these are not co-ordinated incidents,” said Assistant Chief Constable Rob Beckley, head of the Association of Chief Police Officers’ community tensions team. The authorities normally deal with about 50-60 similar incidents a week.

Beckley said police forces were “busting a gut” to respond to the crimes and were making swift arrests in many cases. However, he remained concerned that “a catalytic incident” could trigger something far more serious, such as a full-blown race riot.

Muslim leaders have called for calm and have unequivocally condemned the London attacks. But last week they were criticised for failing to do enough to confront extremists within their own community.

“We have reached a dangerous crossroads and the direction we choose will prove to be a defining moment in our history,” said Shahid Malik, the Labour MP for Dewsbury, home to one of the bombers.

“The knowledge that the bombers were British Muslims . . . has sent us a signal we can no longer ignore, that there is indeed an ‘enemy within’,” he said. “The battle for the soul of the community has begun.”

Tony Blair has invited Muslim leaders to a “crisis” summit on Tuesday to help him “pull up this evil ideology by its roots”.

Under new laws, preachers such as Yusuf al-Qaradawi — who has condoned child suicide bombers — denied entry into America and other European Union countries would face automatic exclusion from Britain.

Charles Clarke, the home secretary, is reviewing his powers to deport foreigners and impose specific conditions on asylum seekers. A separate consultation is just ending on whether imams coming to Britain should have a professional qualification and understand English.

A counter-terrorism bill due in the autumn will create a new offence of “glorifying or endorsing” terrorism. Two further offences being drawn up by the Home Office will mean extremists who provide or receive terrorist training would face prosecution, as would those committing “acts preparatory to terrorism”, such as fund-raising or providing safe houses.

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