The terrorist threat to Britain from home-grown al-Qaeda-inspired radical Muslims is almost as high as it was after the July 7 suicide bombings in London in 2005, according to the latest security assessment.

The threat level has been graded “severe”, the second-highest terrorist-alert status, for the past 12 months. After the July 7 bombings, followed by the July 21 failed plot, the threat assessment was put at “critical”, indicating a red alert. Since then the level was raised once more to “critical”, during incidents in Glasgow and London last year, and then reduced to “severe”.

A senior Whitehall source, however, admitted yesterday: “It's now at the severe end of ‘severe'.” The official said that the police and MI5 were working at full capacity to keep abreast of all suspected terrorist plots. Evidence from intelligence operations and information gleaned from within Muslim communities have indicated that there is an increased level of terrorist-related activity.

“There's lot of ambient activity, some of it sourced to al-Qaeda core [leadership] in the Pakistan/Afghanistan border area,” one source said.

Four special counter-terrorist “hubs” have been established in London, Manchester, Birmingham and Leeds to increase joint police and MI5 efforts in dealing with suspected terrorists. A fifth hub is being planned.

A key al-Qaeda figure, in the view of the British intelligence community, is Rashid Rauf, suspected of being linked to the Heathrow bomb plot of August 2006. Mr Rauf, a British citizen of Pakistani origin, fled from his home in Birmingham in 2002 after his uncle was found murdered, and was arrested in Pakistan in 2006 on suspicion of involvement in the Heathrow plot. He escaped and is believed to be in the tribal regions in Pakistan. “Rashid Rauf is key to us,” the official said.

The Whitehall source added that there was new concern over lone terrorists - individuals who have acquired bomb-making expertise without having any obvious affiliation either to known radical groups in this country or to al-Qaeda masterminds in Pakistan. Detecting lone would-be bombers was a big challenge, the official said, but he emphasised that increasingly active dialogue with leaders of Britain's mosques might help.

MI5 has indicated that about 2,000 individuals in Britain are regarded as being involved in terrorist-related activity, and this figure may now have risen, according to security sources.

The Government, through the Office for Security and CounterTerrorism at the Home Office, is drawing up a new counter-terror strategy, due to be published at the end of the year. There will also be a set of 19 target indicators issued to gauge progress made. Some of these targets will remain classified.

As part of the strategy, the Government is now funding organisations that run anti-Jihad and anti-al-Qaeda websites, in an attempt to counter propaganda put out by extremist Muslim organisations. The Department of Education is also expected to issue guidelines for teachers in schools with a strong Muslim presence to try to get across a more positive message about life and values in Britain.

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