The National Consumer Agency (NCA) is preparing prosecutions against four dealers who are alleged to have "clocked" the cars they were selling.
The agency says that it has received 40 complaints about car-clocking since it started campaigning on the issue last year, and investigations have been launched into 15 of these.
Deputy NCA director John Shine said there was no doubt that car-clocking, the practice of lowering the odometer reader of a car to increase its sale value, was a growing problem.
The NCA had carried out a number of unannounced inspections of garage forecourts as part of a strategy to tackle the problem, Mr Shine said. Moreover, it planned to carry out more raids this year. High-value cars and imported models were being particularly targeted.
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