Around a third of cars on the road have a hidden history, making second-hand purchases a minefield according to research.

Following news that there are 31.4 million cars on UK roads, vehicle information expert HPI said that up to 10.4 million vehicles could have an unwanted or unknown history.

"Unscrupulous sellers use a variety of tricks to bump up the price of an older vehicle and hide a dodgy past", warned Kristian Welch, HPI consumer director.

Finance
With 1 in 4 cars checked with HPI confirmed to be on outstanding finance, this could mean there may be up to 7.8 million cars that are still on finance on the roads. Outstanding finance remains a very real threat when buying a used car, as many don't realise that the debt stays with the vehicle. If the debt remains unpaid, it will leave the new owner at risk of losing the car and the money they paid for it, if the finance company decides to reclaim the vehicle.

Fake ID
Over 6.2 million cars on the roads could have had a plate change, if the car parc follows the trend seen by HPI, with 1 in 5 vehicles hitting HPI's plate change register. This usually reveals an innocent personalised plate, but fraudsters can use a change of plates to hide the identity of a stolen car or an insurance write-off.

Clocking back the miles
5 in 100 cars checked with HPI have a mileage discrepancy, which could equate to over 1.5 million cars on UK roads. Dodgy sellers use clocking as an easy way to increase the price of their vehicle. Not knowing the true mileage could also mean there's a risk of missing critical maintenance tasks, such as full servicing that include important part replacements.

A total write-off
HPI reveals that 4 in 100 cars it checks have been declared an insurance write-off – otherwise known as a total loss. This could translate to over 1.25 million cars on UK roads today. Buyers need to beware of shiny paintwork hiding a dangerous level of damage or inadequate repairs, making it unfit to be on the road, warned the firm.