In his annual report, Lord Carlile QC warned of "poor or unnecessary" use of the special Section 44 powers.

The Metropolitan Police used them 170,000 times during 2008.

Lord Carlile also warned there was little or no evidence that blanket use of Section 44 searches had the potential to prevent a terror attack.

In the strongest criticisms Lord Carlile has ever made of the use of the powers, the peer said that none of the stops in London or elsewhere had led to a conviction.

"I cannot see a justification for the whole of the Greater London area being covered permanently, and the intention of the section was not to place London under permanent special search powers."

http://news.bbc.co.uk/1/hi/uk/8105093.stm