SPECIALIST army surveillance units are helping the police and MI5 to search for potential suicide bombers and their support networks.

The unprecedented joint operation, in the past confined to undercover missions in Northern Ireland, has been under way since the July 7 attacks.

The SAS counter-terrorist squadron, based at Hereford, is understood to be ready to be deployed at three hours’ notice to any location in the country if the police or MI5 pinpoints an address suspected of housing armed terrorists connected to the London bombings.

In Spain, the search for the Madrid bombers last year led police to a house where terrorists blew themselves up after a siege. In a similar situation in Britain, it is likely that the SAS would be called in.

MI5 has also begun a campaign to recruit more women into the newly fornmed Special Reconnaissance Regiment.

The regiment, which was announced in the House of Commons in April, works in teams of four to six to monitor suspected terrorists and draws largely on the expertise of the Army’s 14th Intelligence Company, also known as the “The Det” (Detachment).

The Det, whose operatives usually pose as couples, has unrivalled experience in monitoring republican and loyalist terrorists in Northern Ireland. MI5 has a shortage of women to take on such roles.

Another unit from Northern Ireland, the Joint Support Group, formally called the Force Research Unit, may also be used.

MI5 is devoting a large proportion of the extra funding provided by the Treasury last year in building up its surveillance and international terrorism branches. It hopes to increase its manpower to 3,000 by 2008.

Eight regional MI5 offices are being set up in Scotland and the Midlands, North East, North West, East and South East to liaise closer with police Special Branch forces.

The drive comes as M15 faces questions over its decision not to focus on Mohammad Sidique Khan after he was linked with with terrorist suspects. Last week police said that he was not considered a high priority for investigation last year.

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