By Costas Pitas

LONDON, Mar 1 (Reuters) - Just over 60 percent of recent or prospective car buyers have had their decision-making influenced by Britain's exit from the European Union, including some delaying a purchase, according to a survey by Auto Trader .

British new car sales recorded their biggest drop since 2009 last year, falling 5.7 percent due to uncertainty over potential new diesel charges and weakening consumer confidence since Brexit, an industry body said in January.

Auto Trader, which runs Britain's biggest vehicle buying and selling website, said a survey of just over 4,000 people who had either recently bought a car or were about to in the next six months showed Brexit weighed on many decisions.

"Brexit has made them rethink or reassess their car-buying behaviour, in particular whether or not now is the right time to do it," Chief Finance Officer Nathan Coe told reporters.

The group also said its data, including that the average price of second-hand cars was continuing to rise, showed the credit model which is used by up to 90 percent of new buyers was not leading to a boom.

Most Britons buy a new car using a Personal Contract Plan (PCP) which typically allows them to make monthly payments over three years and then trade in for a new model, with their old vehicle going onto the used market.

The Financial Conduct Authority regulator is looking into whether there is a lack of transparency in such deals and whether they cause harm, after concerns over their sustainability as demand cools and interest rates seem likely to rise.

Some analysts also question how the residual values of diesel cars can be maintained as they come under pressure due to bans, levies and other regulatory crackdowns around the world.

"Prices are still holding up," said Coe, adding that finance deals were needed to encourage motorists to trade into greener models.

"The maths doesn't work if we carry on with declining new car sales to get to a cleaner and more environmentally friendly fleet," he said. (Reporting by Costas Pitas; Editing by Stephen Addison)