The enquiry had collected photographic evidence of damage done to cars by customers who then believe they were overcharged for the repairs.

After showing the photos to three Which? Trusted Trader garage, they reported back they would have charged less than the car hire companies in eight out of 12 instances.

In half of the cases the car hire firms charged more than double the quotes presented by the garages while only eight times out of the 36 did the garages quote the same or more than the car hire companies.

In the worst-case scenario Europcar charged a customer in France £1,154 for a small windscreen chip that could be fixed for £35.

Which? Travel editor Rory Boland said: “It’s outrageous that car hire customers are being made to pay extortionate amounts for repairs that never take place.

"If repairs are required, customers should be sent clear evidence of how costs were calculated.

“Car hire firms now need to clean up their act and be upfront about the real cost of renting a car instead of offering too-good-to-be-true prices, then clawing back profits via ridiculous repair bills.”