Research by the vehicle data analysts has unearthed a number of worrying trends occurring in everyday vehicle transactions.
For every 100 cars HPI checks on behalf of dealers and trade customers, 30 are still on finance, ten have had a previous identity, eight have been clocked, six have been written off due to serious accident damage and one is recorded as stolen by police.
Some cars have more than one discrepancy.
The company said it was imperative that dealers carried out a historical check on vehicles before any money changed hands and warned that criminals were becoming more sophisticated when dealing with cars.
Daniel Burgess, director of HPI's automotive sector, said that while inroads were being made in combating the problem of clocking, advances in technology had helped the criminals and it was still very much on the agenda.
“The type of criminal is changing: they are becoming more professional and while there are fewer of them they are far more sophisticated,” Burgess said.
“I think clocking is bigger than we think it is. Thieves are becoming more sophisticated in the methods they are using and dealers forget that it is still going on.”
Clocking is advantageous to the seller of a vehicle as it can add thousands of pounds onto the value of a car — HPI estimates that for every 1,000 miles the clock is wound back, £75 is added to the value of the vehicle.
Burgess said dealers were becoming better at checking the history of vehicles but were not always as careful when checking for mileage discrepancies.
“They certainly check the finance of a vehicle but with regard to mileage they are not doing as much as perhaps could be done,” he added.
Martin Wright, HPI marketing director, said there was a pressure on dealers from trading standards to maintain their vigilance when checking mileages.
“You have got a group of people who aren't ethical when it comes to selling cars and we have all got to work together to make sure that they don't get away with it,” Wright said.
“We can't take away the technology because it is out there but if we can cut down the clocking market and strangle down the outlets then they can't get away with it and that is the role the trade has to play.”

For every 100 cars HPI checked by dealer and trade customers:
- 30 are still on finance
- 10 have had a previous identity
- 8 carry mileage discrepancies
- 6 are insurance write offs
- 1 is recorded as stolen