Claims by the SMMT that prices of new cars have already fallen by around 10% over the past year were dismissed by Stephen Byers.

In the Trade and Industry Secretary's interview with Automotive Management, he also spurned Nissan's calls for an early entry into the euro in a bid to ensure production of the new Micra at its Sunderland plant.

Mr Byers said: “That's just not true. We have been monitoring new car prices and we have seen little or no evidence of prices falling in the UK.

“Nissan's hesitation in deciding whether it is going to build the new Micra in the UK or not is not down purely to our integration into the euro. “There are a number of factors which Nissan is considering and I know they are looking critically about where the new model is to be produced. As a Government, we have to try to persuade them that the UK would be a good location for the new work. “We will not hastily enter into a new monetary system. We've made our views on the euro clear. While in principle we favour joining a successful single currency, the economic conditions have to be right for the UK before we do so.

“The Chancellor has laid down five individual tests which will have to be satisfied and he will judge those tests early in the next Government. That's a message business understands.”

Ken Keir, Honda UK managing director, said: “It is all a complete mess, especially from the customers' standpoint though Honda can live with the bulk of the recommendations from the Competition Commission.

“But the Department of Trade and Industry has to be aware of the damage this long drawn out affair is having on customers who, after all, are the voters. “It's created an atmosphere where customers will never know whether they feel they are getting a good, bad or indifferent deal. Nonsense about 'rip-off Britain' where prices are supposedly 30% higher is nothing short of headline grabbing by various consumer bodies. “The DTi has to be aware customers are by and large content because they are buying a complete back-up list of services which make the car-using experience pleasurable and safe.

“Safety necessitates investment by manufacturers and dealers and a skill level through the business. “That can't be written off because suddenly someone wants to slash the price of a new car.”