POLICE say they have "no knowledge" of a tracking device being fitted to the car of the July 7 ringleader prior to the London bombings.

It was claimed that detectives probing the blasts had found a device in Mohammad Sidique Khan's silver Honda Accord.

The claims, published by The Sunday Times, suggested that Special Branch officers were monitoring him.

But the Met today denied the claims.

"In view of speculation in the media, the MPS would like to make it clear that we have no knowledge of any technical device being fitted to Mohammed Sidique Khan's car prior to the July 7 bombings," a police statement said.

"We are not prepared to discuss this any further. Investigations continue into the events of last July."

Meanwhile, a computer expert who worked with two of the suicide bombers, also claimed he tried to warn police in 2003.

Martin Gilbertson, a 45-year-old former Hell's Angel and roadie for the rock band Motorhead, told the Guardian at the weekend that he met Khan and Shehzad Tanweer at a radical Islamic bookshop and youth centre in Beeston, near Leeds.

Mr Gilbertson, a non-Muslim, said he was paid to encrypt emails, produce DVDs on children maimed by Americans and secure the centre's computer network.

About Mr Gilbertson's claims, West Yorkshire Police yesterday said: "We do not discuss intelligence matters and therefore we cannot comment."