The expected flood of part-exchanges following the '51' plate change has failed to materialise, according to Manheim Auctions.

Alan Cureton, its dealer distributor director, said: “As potential part-exchange values are decreasing, it is in the consumers' interest to sell vehicles privately to get the best residual value."

He said a downturn in used sales was “worrying”. Used cars are less appealing than normal because of the excellent deals on new.

“Despite predictions for the new vehicle market the value of late year, low mileage vehicles seem to be holding up well, in spite of predictions of a slump. This has not happened due to some prudent planning of stock by manufacturers and daily rental firms. The amount of new stock coming in is at sensible levels but if retailers do not turn these vehicles around due to lack of buyer footfall at dealerships, by the end of the year values could start to fall."