September's all-new registration plate will boost the volume of the used car market as well as the new, with an influx of part exchanges - but dealers are concerned about the quality of trade-ins being offered so far.

“Dealers are already assessing part exchanges due to come in for the September plate change,” said Martin Ward, national research manager for Cap.

“But they are being disappointed by the lack of quality, one to three year old, one owner cars, with around 20,000 to 40,000 miles on the clock.

“Customers looking for nearly new cars in September will have plenty of choice, because daily rental companies are set to defleet many six to eight month old vehicles. They are making way for the high numbers of new cars which they have on order for September, in the expectation that they will command a premium in another six months' time when the first of the new plate cars hit the used market.

“Similarly, leasing companies will be defleeting higher than the usual number of three to five year old cars at this time.

“The abundance of cars available in these brackets will place a downward pressure on values, should retail demand fail to keep up.

“But the main source of good quality, retailable one to three year old stock is the private buyer - and it seems that there will be a shortage, despite the high numbers of used cars entering the marketplace. Those that are to be found are therefore likely to command strong values.”