Both EurotaxGlass's and Cap Monitor, the residual value analysts, agree that used values have already fallen on many of the affected models and new car customers are increasingly considering emission taxes when buying new models.

“We've seen values drop at the top-end on the higher polluting car, like the S-Class and Range Rover, for a little while,” said Jeff Knight, Cap Monitor's forecast manager.

“These changes are likely to impact the middle ground occupied by large saloons, such as the 5 Series and the mid-sized 4X4s such as the Touareg and Discovery. Buyers will be looking at alternatives.”

However, Knight believes some customers facing a £950 VED charge in 2010-11 will continue to choose large engined prestige cars because they can afford the extra payment.

“The extra charge will make these cars more desirable for some buyers as they will be even more exclusive,” he said.

“The value of the heavy polluters has been gently wandering down for a while – they're not falling off a cliff,” he said.

EurotaxGlass's said retailers have been dealing with an average residual value fall of 5 per cent on three-year-old cars each year since 2004 and predicts it will fall by 8 per cent in 2008.

"We should not forget the inherent resilience of the market, which enabled dealers to benefit from continued robust sales activity during the first half of 2007 in the face of five interest rate rises since the previous August,” said Adrian Rushmore, EurotaxGlass's managing editor.

Cap Monitor does not anticipate a significant change in buying patterns at the bottom end of the scale with buyers encourage by the VED waiver on sub 100g/km cars.

“Customers will look at them but will ultimately buy the car that suits their practical needs. Smaller cars are likely to become increasingly popular as second cars,” he said.