Criminals are using eBay to sell stolen and cloned cars, a BBC investigation has revealed.
The vehicles were being sold in Greater Manchester via at least three accounts after having their details switched with legitimate cars.
Among the victims was a retired police officer who lost £17,000 buying a Mercedes from a seller in Rochdale.
He said he reported the incident to the police, but no action was taken. Police said the decision is being reviewed.
Former police officer Graham Murray lost his money after buying a Mercedes C-class in Rochdale two months ago, leaving him "devastated".
He said he reported the case to police and has questioned why the fraudulent eBay sellers have not yet been caught.
'No trust in police'
"The police have known about this gang since January," he said.
"As a former police officer I'm absolutely disgusted. How can you have any trust in the police?"
Car cloning is often used as a method to sell stolen cars.
The vehicle is given the identity of another, similar legitimate car, including licence plates, chassis numbers and accompanying documentation.
It means even if the buyer runs an online background check, the details will appear correct.
Mr Murray, from Dumfries, said the seller had asked for cash on collection, rather than the more usual method of receiving a secure payment via eBay.
The 57-year-old later discovered the vehicle's details had been altered, before police confirmed he had bought a stolen car.
He said: "It was £17,000 just gone, and I knew there was little or no chance of getting this money back, ever."
Another victim, Gordon Alexander, from Forfar in Angus, bought a cloned BMW for £18,300 in January.
Mr Alexander, a garage owner, won the auction and collected it from an address in Rochdale.
He realised he had been conned after the car was taken to a BMW garage for a service the next day.
'Scum of the earth'
"I was absolutely gobsmacked. I've worked hard for my money," he said.
"I've worked every day, and for someone to just take £18,300. They are the scum of the earth. I'm gutted."
Mr Alexander said he was told by police that the BMW had been returned to its original owner in Bury.
An eBay spokesman said the company was yet to be contacted by Greater Manchester Police.
He confirmed the accounts in question had been closed down and added: "Cash on collection is very unusual and we would ask buyers to always pay via the platform when purchasing."
A reporter from BBC Radio Manchester was able to win an auction for a cloned Vauxhall Mokka for £9,600 from one of the suspicious accounts last week.
A car of the same make and model with the same registration plate was then discovered up for sale at a Vauxhall garage in Wales.
The BBC has also informed police of its findings.
An AA spokesman said: "Remarkably, it's quite easy for sophisticated criminals to do all of this, so it's become a real industry. Somebody is making a lot of money."
A Greater Manchester Police spokesperson said: "When we receive a report of any incident, we assess the immediate threat, harm and risk to the public and allocate officers and resources accordingly.
"We do this with full consideration of all the competing demands that we may be facing at that particular time and a decision is then made on how to respond.
"We are currently reviewing the decision made in this case."