Councils are being accused of wasting millions of pounds on motoring perks for staff, with some receiving 65p per mile when using their own car for work.
The Taxpayers' Alliance, a group which lobbies for lower taxes and greater public sector efficiency, found last year's average for UK councils was 56p.
The HM Revenue and Customs-approved level at the time was 40p.
The Local Government Association has disputed the figures, but ministers called the subsidies a waste of money.
Local Government Minister Bob Neill said: "Town halls are wasting millions of pounds of taxpayers' money by these preferential and privileged motoring perks."
Among those local authorities offering the highest mileage allowance were Lancashire, Derbyshire, Cornwall and Warwickshire, according to the Taxpayers' Alliance survey.
Those on the average mileage would have ended up £164 better off for every 1,000 miles driven, the study found.
In all, local authorities paid staff a total of £427m in mileage allowances in 2009-10, up from £402 million in 2008-09, the Taxpayers' Alliance said.
Its director Matthew Sinclair said: "Ordinary motorists who are feeling the pinch will be shocked that council staff are getting such a generous deal for their mileage claims. It simply isn't fair.
"Some authorities have shown that it is possible to save millions by cutting back to the rate recommended by the taxman.
"This is a quick and painless saving that won't affect council services and will ease the burden on households, who've seen council tax double in the last decade."
Minister Mr Neill agreed that "simple changes like clamping down on these subsidies would help councils drive down costs and protect front-line services".
But the Local Government Association said the only council workers able to claim the 65p rate were casual users with the largest cars.
The vast majority, including care givers and social care workers, were on a 50.5p rate, it said.
It added that mileage allowances had been renegotiated since the Taypayers' Alliance carried out its research, and would have been frozen or lowered.
Lancashire County Council said its high ranking by the lobby group was incorrect, but that it was not a surprise as it was one of the largest authorities in the country.
County treasurer Gill Kilpatrick said: "These figures are out of date and don't reflect the current position here in Lancashire, where we will save £2.5m on car travel in the current year."
The council did not reveal its current average mileage payment.
The current mileage rate for 2011-12 approved by HM Revenue and Customs is 45p.