Concern as Ministry of Defence's 'private' police quiz thousands of tourists

Armed street patrols, who are not required to identify themselves as MoD officers, are questioning people queuing for boat trips on the Thames or having their photograph taken in front of Big Ben.

Officers - who are routinely armed with sub-machine guns - say they are targeting those who match "certain profiles or behaviours" to deter terrorist attacks.

Their uniforms make them virtually indistinguishable from other police forces, but unlike regular officers, who are overseen by the Home Secretary and civilian police authorities, the MoD patrols are "under the command" of the Defence Secretary and a committee of civil servants.

Their normal role is to guard military installations and to investigate crimes on the 'defence estate'.

But the 3,500 officers are now able to carry out street searches after they were given extra powers under anti-terror laws.

They are also regularly being called in to provide backup for regular police officers.

Last night, senior politicians expressed "surprise and concern" about the increased public role.

Commons Home Affairs Select Committee chairman Keith Vaz called for an urgent investigation.

He said: "I will be asking the Home Secretary to clarify what these officers are doing, whether they are fully qualified to do this work and how much scrutiny they are under."

The full extent of the use of 'stop, search, secure' procedures has been revealed by MoD Police Inspector Andy Wagon.

Operations were said to include "high-profile foot patrols in crowded places near sensitive or iconic sites" and "plain-clothes spotters sometimes deployed to direct the uniformed patrols and increase their effectiveness".

Writing in a small-circulation Whitehall journal Public Service Review this month, Insp Taylor described a patrol outside the Houses of Parliament.

He said: "During the morning, several persons were stopped and searched under the Terrorism Act . . . Although there is no requirement for police to have suspicion [under the Act], the persons are usually stopped because certain profiles or behaviours have caused the officers to notice them."

The Mail on Sunday can reveal that on average last year the MoD officers exercised their powers about 20 times a day.

An official report says officers carried out more than 3,000 'stop and searches' in 2006.

But yesterday, the force admitted that new figures, to be released in the coming months, would show searches had more than doubled in past 12 months to "in excess of 6,000" in response to the heightened security threat following terrorist attacks on Glasgow airport and car-bombing attempts in London.

The MoD confirmed that its police officers were using their 'stop and search' powers in "predefined areas in Central London and around the country, near military bases, with the prior approval of the Home Secretary and the local police force".

A spokesman said supervision of the force had recently been increased with the appointment of several independent members of its board.