BRITISH agents are operating in the United States to trace links with Islamic extremists from England who recruit Muslims to fight for terrorist groups abroad.

The British-led investigation has played a part in identifying a number of US-based terrorists and helped the authorities in Washington to break up an al-Qaeda cell operating in Falls Church, Virginia.

The agents are particularly keen to discover if the visitors included Mohammad Sidique Khan, leader of the July 7 suicide bombers, who is alleged to have travelled to America’s East Coast to meet fellow militants and stage a series of attacks on synagogues.

Khan was considered such a threat that he was banned from returning to America two years before the attack on London, according to a book written by a US intelligence specialist.

The disclosure, made by the award-winning author Ron Suskind in an extract from The One Percent Doctrine in The Times yesterday, led to calls for a full public inquiry into intelligence lapses before the attacks on July 7 which killed 52 people in London.

Intelligence sources in America insist that the man they were alerted to was Khan.

However, Tony Blair’s spokesman said the claims would not lead to any further investigation by the Intelligence and Security Committee, which last month cleared MI5 of serious errors, or any other form of inquiry. “The [Security and Intelligence] Committee’s conclusion is that there was not an intelligence failure,” he said.

The Conservatives have called for an independent inquiry into the July 7 bombings, while the Liberal Democrats and victims’ relatives want a full public inquiry.

Neither the FBI nor police would comment on the investigations into Khan’s alleged visits to the US in 2002, but, in Falls Church yesterday, residents blamed “foreign agitators” for encouraging young men from the city’s Muslim community to join extremist groups linked to al-Qaeda.

In the Falls Plaza shopping mall, most preferred to chat about their historic city’s latest civic award for its floral displays and not its reputation as the jihad capital of America.

Over the past few months, 11 men who regularly attended the same Islamic Centre in Falls Church have been convicted of terrorism charges. Seven reportedly went to training camps in Pakistan, including one used by Khan.

Their trials exposed a network stretching from this placid commuter belt serving the US capital ten miles away, passing through British cities and on to jihadi camps in Afghanistan and Pakistan.

A twelfth man from this city of barely 11,000 residents, Ahmed Omar Abu Ali, was jailed for 30 years in March for plotting to assassinate President Bush and being a member of al-Qaeda. FBI investigators claim in The One Percent Doctrine that Abu Ali, 24, was in regular e-mail contact with Khan.

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