The cost of running a car has continued to fall while fares on public transport have risen sharply.
Despite the Government's pledge to lure people out of their cars, figures yesterday showed that motorists spent a weekly average of £103.58 between April and June - 1.7 per cent, or £1.83, less than in the first three months of the year.
It contrasts with large fare increases for rail and tube passengers this year - up to 7 per cent on some overground lines and 5.3 per cent on the London Underground. Bus fares in London are also increasing as part of an above-inflation average rise of 3.6 per cent.
According to the RAC's Insure Motor Index the drop in driving costs was due to a combination of economic factors.
A spokeswoman said: "The falling prices of new cars over recent years, low interest rates, slower depreciation of car value, stiff retail competition and cheaper fuel have contributed to lowering costs."
Steve Hounsham, a spokesman for Transport 2000, an independent body concerned with sustainable transport, said cheaper car travel discouraged people from using public transport.
"The costs of public transport compared to car travel do not support the Government's notion of getting more people on buses and trains," Mr Hounsham said.
"It takes more than providing good public transport improvements to get people to stop using cars.
"We have to make the driving substantially more expensive than public transport for that to happen, something that has yet failed to happen.
Research for the pressure group shows the real cost of motoring has generally remained static or fallen since 1975, while the cost of using public transport has risen by up to 80 per cent.
Increases between January 1987 and May 2000 for all motoring costs amounted to 82.4 per cent, while bus fares rose by 102.7 per cent and train fares by 105.8 per cent.Reuse content