A campaign group is demanding tough new measures to crack down on cowboy car mechanics.

The National Consumer Council (NCC) says half the garages in the UK offer poor service. Shoddy repairs and car servicing cost motorists an estimated £4bn a year, the group says.

The extent of the problem is revealed in a report released today, At a Crossroads, which warns that poor standards put motorists' safety at risk and can push up prices.

It concludes: "The consequences of poor standards in this industry are serious. Shoddy workmanship on a car can cause death or serious injury.

"The financial loss that consumers suffer collectively is also on a massive scale."

The NCC first threatened action against the car repairs industry two months ago. It and its Scottish and Welsh sister bodies announced plans for a "supercomplaint" in April, after it found people were "consistently and comprehensively" getting a bad deal from mechanics.

Since then, the NCC says, some progress has been made, as the largest trade body, the Retail Motor Industry Federation (RMIF), now plans to apply to the Office of Fair Trading (OFT) to agree a code of practice.

The NCC welcomed the RMIF's plans and said it wanted both the RMIF, and the Scottish Motor Trade Association (SMTA), to agree a self-regulating code of practice with the OFT by March 2006.

Philip Cullum, NCC deputy chief executive, said the two trade bodies represented more than 10,000 garages - almost half of all those in the UK.

The NCC said if either body missed this deadline, they should face government regulation to improve standards.

The consumer watchdog has put forward two options for regulation: a levy on garages to help fund undercover quality checks, or a licensing scheme for mechanics and/or garages.

It wants the DTI to create an independent complaints system for the whole car servicing and repair sector.

"The government shares the NCC's view on self-regulation," a DTI spokesman said. "We want, and expect, to see all those concerned, including the RMIF and SMTA members, to move forward in achieving OFT approval for codes in this sector."

Responding to the report an RMIF spokeswoman said: "I am pleased to confirm that the RMIF is working with the OFT on a new code of practice to raise standards."

Douglas Robertson, chief executive of the SMTA, welcomed the report. He said: "The SMTA remains committed to improving the relationship between our members and the consumers.

"We remain committed to the reduction in consumer detriment and we are continually working towards that goal in what we believe to be a realistic fashion."