A survey for the Consumers' Association magazine Which? found that an alarming number of salespeople could not, or would not, answer basic questions about the models and the finance packages on offer.
Many of them failed to provide written finance quotes when asked, which is a criminal offence.
Only seven out of 64 dealers visited were able to answer all the retailers' questions correctly and helpfully.
Manufacturers, who have almost complete control over who sells their cars, failed to direct to their nearest dealer many of the customers who phoned a helpline. Peugeot got it wrong half the time.
Dissatisfaction with dealers is not new. In January 1996 more than 45,000 motorists phoned the Korean car giant Daewoo after an advertisement offered them a car free for the year if they had suffered at the hands of other drivers.
Eight researchers for Which? visited dealers in the Midlands, the north west and the south east of England, posing as new car buyers. In each area they went to the main dealer for the biggest makers - Ford, Vauxhall, Rover, Peugeot, Citroen and Volkswagen.
In more than a quarter of cases the researchers said they would not be happy to buy a new car from the dealers they had visited.
They found bored staff who fobbed customers off with leaflets. A researcher who went to one Rover dealer in Birmingham said: "One salesman went out for a cigarette. I felt we could be interrupting their quiet life". .
Three of the five female researchers felt that some salesmen were reluctant to deal with women. Only one salesperson out of the 64 dealers was a woman.
All new car dealers offer finance packages, and under the Consumer Credit Act they must provide specific written information if requested. Yet when the researchers asked half the dealers for a written quote, 18 refused, or gave incomplete information, and only five produced documents which were legally correct.
Which? editor Helen Parker said: "Clearly, you cannot rely on dealers as a source of information, let alone advice.
"The reason given by manufacturers for their exclusive dealer arrangement is that only their dealers can provide expert advice on their cars. But if manufacturers will not monitor those dealers properly, the exclusive arrangement must be taken from them."Reuse content