At least 700 people suspected of being involved in al-Qa'ida terrorist plots have been identified by MI5 and the police, The Independent understands.
There has been a threefold increase in the number of terror suspects identified by the security service, MI5, since the 11 September attacks in the United States in 2001, security sources have disclosed.
Details of the rise comes as the Government faces a charge of "whitewash" tomorrow over the scrutiny of the intelligence into the 7 July 2005 London bombings, in which 52 passengers were killed as well as four terrorists. The Tories believe the publication of two major reports, due out tomorrow, will fail to answer the question of why the suicide bombers managed to evade detection.
A report by the Commons Intelligence and Security Committee will find no evidence that MI5 or MI6 could have prevented the attacks by a team of British terrorists. The report will raise several questions over the effectiveness of Britain's anti-terrorist operations. It will suggest that intelligence-sharing between Britain and Pakistan is poor, and question why the level of security alert was lowered just before the bombings.
Despite being cleared of blame, the security agencies are certain to come under renewed criticism with the confirmation that they had two of the bombers under surveillance in the months before the attack, and the ring leader, Mohammad Siddique Khan, visited a terrorist training camp in Pakistan.
MI5 argue that they had to prioritise their investigations and could only target the key players in the bomb plot they were investigating, which did not include Khan.
The scale of the problem facing Britain's counter-terrorism agencies is highlighted by new figures of suspected terrorists currently under investigation in the UK.
Since the 2001 attacks in the United States, the number of identified al-Qa'ida supporters living in Britain who are considered a threat to national security has risen by 300 per cent, according to security sources. Although a total number has not been confirmed, sources have indicated that it is in the "high hundreds" and "far more" than the most recently quoted figure of 400. A Whitehall source last night put the total at "at least 700" and the police have quoted a figure of 200 in 2001. A security source said: "We are talking about radicals or plotters who would be of interest because of their potential threat to national security.
"There has been a 300 per cent increase since 9/11 in those types of individuals that we are looking at and are concerned about."
A Whitehall source added: "The service [MI5] is currently at a very high level of operational intensity in investigating plotting leading to mass casualty attacks in the UK.
"The current picture is very much like an extremist soup with a number of overlapping networks with a common cause. But these networks aren't attached to each other.
"The picture is changing all the time. Many of the plotters are homegrown and currently living in the UK."
Whitehall sources also disclosed that Islamist extremist groups in Pakistan have stepped up efforts to recruit young British Muslims visiting the country.
The Home Secretary, John Reid, will tomorrow make a statement to the Commons setting out a "narrative" which highlights the need to tackle Muslim fundamentalism in Britain.
The Home Office narrative suggests that the four suicide bombers were "self-taught", picking up tips on bomb-making through the internet. It also says there is nothing to suggest a "fifth bomber" was involved.
In a second, separate report, the intelligence committee of MPs will say that there was no evidence of a formal link between the British bombers and al-Qa'ida.
It will criticise MI5 for lowering the alert against terrorism a month before the 7 July attacks, but will conclude that there was no evidence that a bombing campaign was about to be mounted.
The intelligence-sharing between Britain and Pakistan will be criticised. Despite having a large base in the Pakistani capital, Islamabad, MI6 were unaware of visits to the country - and contacts with Islamist groups - by two of the suicide bombers, Khan and Shahzad Tanweer.
The MPs will also protest over the resources allocated to the security services in recent years. The new Home Secretary is expected to argue that such shortfalls are being urgently addressed. MI5, MI6, and the Metropolitan Police's anti-terrorist branch are all currently undergoing big recruitment drives in order to help plug the intelligence gaps.
Government sources say they are braced for criticism after the publication of the two reports. One source said: "Of course there are unanswered questions - there are still things we do not know."Reuse content