One in three used cars still has potentially hidden history, according to an analysis of over 10 million checks carried out by HPI.

The most common danger is outstanding finance, with one in four cars still having debt attached to them. A new buyer could be liable for all outstanding finance and if he or she can't pay it, the car could be reclaimed with no compensation.

HPI reports that 19 cars every day are found to be stolen in the process of its checks. Many others are never checked and go undiscovered. Other hazards include buying an insurance write-off that has been illegally repaired - a potential death-trap.

A further 6% have been `clocked', where the mileage is falsified and reduced to raise the apparent value of the car. This can be very costly to fall foul of, because it can mean missed or inappropriate services, late essential maintenance and potentially critical damage being caused.

One in five has had a number plate change. Many cars have been given personalised plates but fraudsters can use them to try to hide a car's past. The registration number should always be checked against the car's chassis number; a service HPI includes in its checks.

"As our latest figures show, innocent buyers continue to be caught out fraudsters," Kristian Welch, Consumer Director for HPI said. "Consumers need to remain vigilant and an HPI Check report can give them very real protection, including up to £30,000 financial reimbursement [subject to terms] should the information we provide being incorrect or incomplete.

"If it looks too good to be true, it probably is. Don't take the risk."