Service costs vary hugely between franchise dealers and independents

Main dealers charged �84 an hour for labour, while independents charged �40 on average, Warranty Direct found.

The group accused franchise dealers of "rip-off" pricing and charging clients based in the south of England the most.

In response the body representing dealers said their charges were higher because they spent more money on training and the latest equipment.

Just because you have bought an expensive car, it doesn't automatically mean you should take some of the rip off rates being charged on the chin Duncan McClure Fisher, Warranty Direct

Charges varied

Warranty Direct said it had found labour charges were highest in London and the south-east of England and lowest in Scotland and Northern Ireland.

One BMW garage in London charged labour at �158 an hour, nearly four times the cost of an average independent garage.

The group also found that service charges varied according to the age of the car - owners of vehicles under three-years-old would pay 20% more than those with a four-year-old vehicle.

And some dealers were even charging different rates depending on the type of car.

One Land Rover dealer charged �90.48-per-hour for work on a Range Rover car, compared to �69.37 for a cheaper Land Rover Freelander.

The most expensive cars to get fixed at a franchise dealer BMW �158.63 Audi �146.8 Land Rover �129.95 Jeep Chrysler �129.35 Mercedes �123.38 Source: Warranty Direct

Unsurprisingly, prestige car brands such as BMW, Mercedes and Land Rover were the most expensive to service.

"Just because you have bought an expensive car, it doesn't automatically mean you should take some of the rip-off rates being charged on the chin," Duncan McClure Fisher, Warranty Direct managing director said.

"The fact is the job done is the same in Norwich as it is in London, but you'll save over �65 an hour if you're an Audi owner."

In response, Matthew Carrington, the chief executive of the Retail Motor Industry Federation (RMI), said that they spent more than independent garages on staff training, new equipment and customer benefits such as a free courtesy car.