The AA wants the practice made compulsory, but is meantime urging managers to record mileages to make it easier to catch and prosecute offenders.The call comes as fleet operators shed thousands of vehicles for August P-plate cars, giving clockers the chance to pick up auction vehicles and wind back odometers before selling on.

The Institute of Trading Standards Administration believes clocking costs consumers £50 million a year, but despite repeated calls for a tightening of the law on transfer of ownership, the Government has still to act. AA vehicle inspections operations manager Alan Welsh said: 'By filling in mileage on the tear-off strip of the V5 registration document and sending it to the DVLA, fleet managers can stop clockers defrauding buyers of thousands of pounds from just one vehicle.'

The British Vehicle Rental and Leasing Association last year set up a mileage database on which members can register vehicle mileages. Development manager Derek Jones said around 470,000 - or 35% of members' vehicles - were registered and of 5,700 enquiries received, 90 led to identification of clocked vehicles.