Roger Woodward, managing director of the online auction company, says that canny dealers used to buy at the end of December in order to take advantage of rising prices in the early months of the new year but believes that they will be more cautious this Christmas. He explains: 'The VAT rise in January means they will have to absorb a 2.5% price increase on most cars sold at auction or raise their forecourt prices.

'We think many will stick on their hands or only bid for bargains. Vendors need to be realistic and take the money that’s on offer if they want to see their cars sold before Christmas.'

However, used car values at auction are likely to remain relatively strong in the medium term as the wholesale market reacts to a shortage of good quality stock.

Mr Woodward said: 'You have got to remember that, by mid-2008, many fleets had simply stopped buying new cars. These vehicles should be coming to the used market in 2011 and they would have been the bread and butter of the used car forecourt.

'New car sales to fleets were down by 7.1% in 2008 and a further 20% in 2009. New car sales to private buyers were down almost 15% in 2008. So, where are next year’s used cars going to come from?'

He added: 'We think 2011 is going to prove challenging in the used car market for both fleet vendors and traditional trade buyers such as car supermarkets and dealer groups. There is no doubt there is going to be a continuing shortage of good quality, retailable stock and that means auction values will be strong for the right vehicles.

'We expect the end result to be a widening at auction of the value gap between good quality, read-to-retail stock and average cars. Vendors should be very wary of holdings onto cars for too long or presenting cars for sale in poor condition.'

CD Auction Group is already seeing a rise in the average age of vehicles it sells from some of the UK’s major trade vendors through its online auctions. The average age in 2008 was 35 months; in 2009 that stretched to 37 months and, in 2010, the average age of cars sold is 41 months.