Too little is being done to stop car repair garages carrying out shoddy work at the expense of the motorist, a standards watchdog has said.
The British Standards Institute wants a code of conduct, using something like its Kitemark logo, for garages.
Last year there were more than 15,000 complaints about independent garages to the government's advice line.
Two years ago, the BSI launched a Kitemark for garages, but only 150 of an estimated 18,000 have signed up.
The Society of Motor Manufacturers and Traders has also told the BBC it plans to launch a new industry-wide code of conduct in May.
The BSI says it wants to improve the image of the industry, which sales and marketing director Ian Harper said had "monumentally failed" to get serious about the issue.
Mr Harper said: "The Kitemark can throw a huge amount of confidence back to the consumer."
He added: "If the consumer is going to be protected, I think some form of compulsion might be a way forward, but we're not directly calling for it now."
Car servicing and repair has been in government advice line Consumer Direct's top 10 complaints for the last couple of years, and there was an 11% increase in complaints about car servicing between 2006 and 2007.
And the Department of Trade and Industry estimates that consumers lose £4bn a year as a result of shoddy work and poor service.
Last year the National Consumer Council (NCC) issued a plan for the car repair trade to end "scandalous practices".
It said the garage industry must adopt codes of good practice, so that all car owners could find a reliable garage to repair their vehicles.
It warned that if the industry was not seen to be making significant progress it would urge the government to bring in a system of formal regulation for car repairers.
The BSI Kitemark logo has been used since 1903 to assure consumers of all kinds of products and services that they have been independently assessed.