LONDON - At least 700 people suspected of being involved in al Qaeda terrorist plots have been identified by MI5 and the police, it has been reported.

There has been a threefold increase in the number of terror suspects identified since the September 11 attacks in the US in 2001, MI5 has disclosed.

Details of the rise comes as the Government faces a charge of "whitewash" today over the scrutiny of the intelligence into the July 7 London bombings last year, when four bombers killed 52 people. The Tories believe the publication of two major reports will fail to show why the bombers managed to evade detection.

A report by the Commons Intelligence Committee will find no evidence that MI5 or MI6 could have prevented the attacks. 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.

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 US, the number of identified al Qaeda 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 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 said the total was "at least 700". Police quoted a figure of 200 in 2001.

A source said: "We are talking about radicals or plotters of interest because of their potential threat to national security.

- INDEPENDENT