The breakdown company’s most comprehensive survey of motoring costs, including depreciation, maintenance, road tax, insurance and the cost of borrowing, found that the average driver spends £14 a day to keep a car on the road.

Even those with the most economical models, such as the Citroën C2, spend almost £3,000 a year. The worst petrol guzzler in the survey, the Porsche Cayenne, costs its owners £19,000 a year to run, or £1.58 per mile over the average 12,000 miles a year.

Average weekly household expenditure on motoring has almost doubled in real terms in the past quarter of a century, with spending at today’s prices rising from £36.70 in 1982 to £62.60 last year. The fall in recent years in the purchase price of new cars has been more than eclipsed by the rising cost of fuel. Petrol prices have fallen since their peak in October, but are still almost 10 per cent higher than a year ago.

The average cost of petrol across the country is now 88.39p a litre compared with 81.59p on January 1 last year.

The Petrol Retailers’ Association predicted yesterday that petrol prices would soar back above 90p a litre over the next few weeks and by the summer would match October’s peak, when many service stations were charging more than £1 a litre.

However, the RAC found that the cost of depreciation far outweighed the cost of fuel, with the average car losing £1,987 a year, or £38 a week. This is the average annual depreciation over the first three years of the car’s life.

Rates of depreciation varied greatly across the 17 cars in the survey. The Cayenne loses the most, falling by £8,900 a year from the new purchase price of £81,000. Yet, once all the costs are factored in, the most efficient vehicles are not necessarily the cheapest. The Toyota Prius costs only £787 to fill with petrol for a year, almost £500 less than does a VW Golf. The petrol-electric hybrid also saves its owners £60 a year in road tax compared with the Golf.

But the Prius depreciates by £2,733 a year, compared with only £1,530 for a Golf. Overall, the Prius is more than £1,000 more expensive to run per year.

Figures for new car sales due to be released tomorrow will show that rising fuel costs have failed to dampen enthusiasm for the largest, least efficient cars. Sales of 4x4s rose to a record 185,000 last year, more than double the number sold in 1995. The environmental lobby group Transport 2000 said that the true costs of motoring should be made much clearer to drivers to help to persuade them to use public transport.

Stephen Joseph, the group’s director, said: “If there was a meter in each car showing the total costs of car ownership then drivers would be much more inclined to consider catching a bus or cycling. Bus industry research shows that most people don’t even take into account the cost of petrol when deciding to make a car journey. The cost of parking at their destination is the only thing which registers.”

Mr Joseph said that motoring costs would have to rise significantly to have any impact on traffic levels.

Motorists have been shielded in part from rising prices by the Government’s decision to freeze fuel duty for five of the past six years. Tax is now 12 per cent lower in real terms than it was in 1999. In real terms, the cost of motoring has risen slightly since 1990 but is still cheaper than it was in 1980.