Labour rates of up to £170 an hour are charged by some garages for car servicing, a survey of more than 3,000 establishments found.
The highest hourly rates were in London, but £100 an hour was reached in 80 per cent of British regions.
Labour rates ranged from an average of £116.53 an hour at London franchised dealers to £32.12 at independent workshops in Lanarkshire, Scotland.
The highest hourly rate found in the survey by Warranty Direct, a company which insures against parts and labour costs, was £170.61 in London. Even in Lanarkshire the highest rate reached £112.80.
A spokesman for Warranty Direct, Duncan McClure Fisher, said: "After a couple of years of excessive rises, mechanic labour rates have started to stabilise, but it is obvious that there is still a major gulf between regions, and between independent and franchised garages.
"The latest findings show that garage rates are still extortionate, but motorists can help themselves by asking how much they charge an hour. Unfortunately, once you get the bill, it's too late to yell."
The disparity between franchised and independent labour rates was starkest in the West Midlands. The average overall there was £66.35 an hour, but the charge was as high as £117.45 at franchised garages, and as low as £23.50 at independent workshops.
The five most expensive regions for franchised dealers are shown in the panel, with the five least expensive being Cornwall, Angus, Cumbria, North Yorkshire and Aberdeenshire.
The highest rates
Average hourly rate: £116.53
Top rate: £170.61
Average hourly rate: £110.54
Top rate: £158.63
Average hourly rate: £108.15
Top rate: £158.63
Average hourly rate: £99.76
Top rate: £141.61
Average hourly rate: £97.86
Top rate: £122.20