Nearly three-quarters (70%) of complaints received by the Office of Fair Trading's (OFT) Consumer Direct division during the January to September period of 2011 related to faulty vehicles, according to new figures.
Over 13% of the 56,000 complaints were lodged by motorists who felt a seller had misled them, while substandard services accounted for nearly 7% of the motoring problems reported.
The latest figures were revealed by the OFT as part of its Know Your Consumer Rights campaign, aimed at making people aware of the risks involved when buying a second-hand vehicle.
The OFT found in its 2010 study that used car buyers were losing a total of £85 million a year due to issues that sellers failed to fix.
Such faults could possibly lead to an increase in the number of road accidents, which could result in more car insurance claims.
Michele Shambrook, from Consumer Direct, said: "We want to help people understand their rights when buying a used car from a dealer and we are working with the industry and local authority trading standards to get this message across.
"Dealers who fail to treat customers fairly or sell cars that are defective could face enforcement action."
© Press Association 2011