One in five of the 3.6 million people buying a secondhand car from a dealer each year experienced a problem, according to a damning report by the Office of Fair Trading.
The damning verdict on the Britain's £24bn secondhand car market follows a nine-month study into the industry.
BBC website readers have been sending in their experiences about buying secondhand cars.
I own a dealership myself and I am shocked by the comments made in this article. Firstly the OFT or HPI are telling my customers that 1 in 8 of my cars have a mileage discrepancy, which I can assure you is not true. This so called statistic does not take into account when people using HPI type in the wrong mileage, which is human error, I have seen this done plenty of times.
My next argument is this article is also stating that 'reputable' dealers are having a problem with 1 in 5 customers. This is highly likely due to the fact that they are USED cars and there are a lot of things that can go wrong.
However, when a customer has a problem, nine out of ten they go away satisfied that we have rectified the problem. I'm also sure it is the same across nine out of ten dealerships when they have a customer come in complaining about a fault.
Even going to a 'reputable' dealer means nothing. I was promised a £500 trade in on the car, reduced to £250 when it came to signing papers, and then - still no service history as promised four months after the event. Oh, and they've said I've lied about it all too when I complained. Still, I suppose putting people off buying a car at all has got to be good for preventing climate change...
I bought a car in December last year from a small local car dealer and part exchanged my own car. It broke down on a motorway two weeks later with engine failure and was recovered to my home. I contacted the AA and took some legal advice, then informed the dealer of the problem. I did not even need to mention my rights as he sorted it out with a refund in cash, as he had already sold my car after some price negotiations. A happy end for once.
Marc, Blackburn, Lancashire
A few years ago I purchased a Toyota Previa from a secondhand dealer in Baldock, now closed down. They said they would do a full service but when I collected the car I checked the colour of the oil and it had not been changed, the oil filter was not new. But the service record book had been marked as serviced. So I refused to take delivery. They made excuses as to why it had not been done. A few days later I collected the car, checking the service had been done. The car was sold with a three month warranty. In a month it started to run rough at low speed once it was warm. I took it back explaining the problem.
They claimed to have fixed it by draining the fuel and replacing it - charging me for this as it was not their fault. It still ran very rough so I took it back to them. I felt they were not doing anything so I stuck a small piece of selotape on the bonnet, just to see if it had been opened. On collecting the car the salesman said it was fixed - must be very clever doing this without opening the bonnet I told him. I was getting nowhere so I took it to the main dealer in Cambridge, they charged me £160 to clean the throttle sliders, something which is done on every service according to them. I tried to get compensation from the dealer, but they denied any wrong doing on their behalf. Tried to take it through small claims court only to be told the dealer had sold its plot for development and I would get nothing.
Richard, Cambridge, England
I bought a Honda Civic 1.4 SE a couple of years ago. I drove it home (300 miles) and it began to make some strange noises, it turned out the gearbox was damaged. The independent dealer refused to fix it and in the end it cost me £1100 to repair! Even after sending letters to the dealer, that trading standards recommended I send, nothing ever happened. I never saw a penny of my money.
Daniel, Plymouth, England
I've had good experiences buying cars from private dealers, national dealers of new and used cars, and local secondhand car dealers. But the industry could do themselves a favour by promoting RMI membership and making it recognisable and desirable for consumers (like a CORGI approval for gas fitters).
Also remember that there is an economic theory that explains that many second hand cars are 'lemons'. That is, the cars for sale are more likely on average to break down because reliable cars are kept for longer by their owners and not sold so frequently. So everyone needs to take care buying a used car.
Neil, Richmond, UK
A few years ago I bought an R-reg secondhand car from a secondhand dealer in Bristol, knowing there would be (and the test drive proved there were) a few problems with it. My now ex-fiance was a mechanic and we felt we were in a better state than most to purchase a secondhand car.
When I went to pick the car up, the MOT had been mislaid, apparently left at the home of one of the dealers when he borrowed the car. Two weeks later it was still nowhere to be found so I checked online - the car had no MOT! I took it back (they had removed a headlight bulb too!) and they sent it for testing - it came back still with problems and no headlight bulb so I called VOSA to retest it (they apparently followed this up as it failed) and I made a formal complaint to OFT.
I felt that I had no one to turn to and in the end had to pay not only for the purchase of the car but also for disposal of the car (I had by now broken up with my fiance and found the cost to get the car back on the road too high) and ended up about £1000 out of pocket. It would have been much more if I had been pulled over by the police with no MOT.
I went and bought a two-year-old car from a VW dealership after this - much more expensive and on finance, but I felt that they weren't as "untouchable" if I had problems!
Emma, Huntingdon, UK
I'm currently looking for a car, and would offer the following advice: Do not accept any dealer's word on the service history of the car. I called Mercedes Benz to get verification of service history, which didn't match what the dealer claimed. Make the effort to verify everything, and do not be afraid to ask to see evidence of any/all reports they claim to have made.
I bought a secondhand car from a main dealer - part of a very large group and the car was a bag of bolts. From failed power steering (twice), failed water pump, fake MOT - issued by the same dealer, and seriously defective brakes, all within a week. It was a four-year-old car at the time. Was I offered a refund? Not a chance.
As soon as they had my money they were not interested in fixing any of the problems. Consumer Direct could not help me, SMTA would not help me as the group is a major business and the DoT could not have cared less about the fake MOT. What is the point of the OFT? I subsequently bought a car from an independent garage, nine years-old and have never had even a hint of a problem with the car or the garage, they couldn't do enough to help me.
Main dealers? I thought Dick Turpin was dead.