Birmingham City Council has admitted the picture quality of the cameras is so poor that registration plates often cannot be identified.

This means that motorists whose cars are photographed by the four cameras, which are switched between 40 sites on major roads in and around the city, cannot be prosecuted.

Bill not paid

The council said on Monday that it was refusing to pay the final £150,000 bill for the cameras until the problem was fixed.

Chris Maddox: "The picture is blurred"

The cameras were launched last July, and appeared to work effectively until October when police first found that on occasions, number plates caught on camera were too blurred to read.

Birmingham City Council's Transportation Spokesman Chris Maddox said the manufacturers, Serco Technology, based in Basingstoke, were now carrying out tests and working on improving the picture quality.

He said: "What's happening is that on occasions, when the police need to get the information for the registration of the vehicle, the picture is in fact blurred and they can't get the exact number, which has to be spot on.

Motorists are escaping prosecution

"We are working closely with the manufacturer to overcome this hiccup.

"It is a problem which is occurring elsewhere in the West Midlands, and perhaps in the country.

"I understand it is to do with the combination of the speed of the vehicle and the speed of the shutter lens which have to be in very good sync.

'Disappointing'

"They are working intermittently, but it is very disappointing because it has been proved that speed cameras are a major deterrent to speeding motorists."

No one from Serco Technology was available for comment.

The problem with Birmingham's speed cameras follows reports last year that thousands of motorists were getting away with speeding because police did not have the money to take them all to court.

The Chief Constable of Avon and Somerset Police, Steve Pilkington, said speed cameras were so effective that if his force prosecuted everybody they caught he would have to take officers off the beat.