Mileage discrepancies now affect almost 10 per cent of popular second hand vehicles, according to HPI. Volume family models pose the greatest risk but 'clockers' are beginning to target a broad range of vehicles including MPVs and 4x4s.

HPI's analysis of its National Mileage Register (NMR) shows that 1.4m vehicles currently have discrepancies or odometer changes, out of a total 70m on the register. The Ford Escort is the most clocked with over 144,000 examples, while more than nine per cent of Vauxhall Calibras have a discrepancy.

“Cars are now built better than ever and are designed to withstand increasingly high mileages. This plays into the hands of the 'clockers' because many of the tell-tale signs may not be present,” says Martin Brassell, director of HPI.

“The value of NMR checks and investigations has never been greater and dealers must realise the importance of protecting themselves and their customers.”

Ex-fleet vehicles such as the Ford Mondeo are popular, with almost 55,000 known clocked vehicles on the NMR. The Ford Galaxy is the most clocked MPV while the BMW 3-series tops compact executives.