Police are stopping 366 people every day in London under stringent anti-terror powers described by the official security legislation watchdog as “a significant intrusion into personal liberties”.

The number of random checks carried out in the capital increased fivefold to almost 11,000 last month in the aftermath of attempted car bomb attacks, when the threat level was raised to severe.

Scotland Yard said yesterday that it was encouraging beat officers to use their stop-and-search powers more often and more widely to deter further terrorist attacks. Commander Rod Jarman predicted “an increase in overt counter-terrorism activities by the police over the coming months”.

Street checks will take place across London, with particular focus on crowds at airports and mainline stations that have been targeted by terrorists in the past, and iconic landmarks that al-Qaeda has repeatedly identified for attack.

Checks will be carried out in a way that is highly visible to Londoners and visitors alike and could have an impact on the tourist trade.

Before last month the monthly average number of checks was 2,114 and in 2006-07 the annual total was 25,374.

Scotland Yard said that 54 per cent of those stopped last month were white, compared with a 71 per cent white population in Greater London. The proportion of people of Asian ethnicity stopped was 24 per cent – double the percentage in the capital’s population.

The surge in the use of the power, combined with the Prime Minister’s recent announcement of a border force and extensive electronic screening of travellers, is increasing civil liberties campaigners’ concerns. A spokesman for the Campaign against Criminalising Communities said: “More and more people are being harassed and threatened with prosecution under antiterrorism laws if they refuse to cooperate with being searched. It’s another step on the way to a police state.”

Section 44 of the Terrorism Act 2000 authorises police to search any person or vehicle in a designated area without the need for reasonable grounds for suspicion. Greater London has been designated as an authorised area for several years and the power to stop and search is reviewed monthly by the Home Secretary.

After the terrorist incidents in London and Glasgow at the end of June, the power was extended nationally.

Lord Carlile of Berriew, QC, the independent reviewer of terrorism legislation, raised doubts about the effectiveness of the power in his report on the 2000 Act in June.

He said that Section 44 was used too much, when it ought to be used sparingly. His report added: “I remain sure that Section 44 could be used less and expect it to be used less. There is little or no evidence that the use of Section 44 has the potential to prevent an act of terrorism as compared with other statutory powers of stop and search.”

But Scotland Yard has conducted its own review of the search power and concluded that it should be employed more widely and more often.

Counter-terrorism commanders believe that it is unlikely to lead to the capture of a terrorist, but will have a significant deterrent effect. Terrorists are known to conduct reconaissance and dummy runs, and with highly visible spot checks taking place they may be deterred.

A police source said: “If it disrupts their activities that will give our covert methods of tackling terrorism more time to detect and detain people.”

Separate figures on covert operations, also released by Scotland Yard, show that it spent £2.2 million last year on informants assisting investigations into organised crime, firearms use and terrorism.

Inayat Bunglawala, assistant secretary-general of the Muslim Council of Britain, said: “It is perhaps unsurprising that we have seen this massive increase in the number of stop-and-searches carried out in the immediate aftermath of the attempted car bomb attacks in June.

“However, questions remain regarding the actual effectiveness of such a strategy based on disruption – given the very low number of charges brought as a result – and whether it is actually doing more harm than good.”

Gareth Crossman, of Liberty, said: “Thousands of Terrorism Act stop-and-searches have produced hardly a single terrorism arrest. When not targeted against specific threats, Section 44 undermines community relations and wastes police resources.”

Bob Cotton, of the British Hospitality Association, said that high-visibility policing appeared to reassure overseas tourists but deter domestic visitors to the capital. The June car bomb incidents had “no impact at all” on visitor numbers, he said.

Few search arrests

22,700 stop-and-searches were carried out by officers from the Metropolitan Police in 2006

27 led to terrorism-related arrests

1,126 arrests under the Terrorism Act 2000 between 2001 and 2006

117 of those were charged with terrorism legislation offences

104 were charged with terrorism legislation offences and other criminal offences

Sources: Times database, Muslim Council of Britain

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