Fuel bills and other motoring costs are due to soar and could force many drivers out of their cars.
Research by the Society of Motor Manufacturers and Traders (SMMT) says many families could be badly stung by big increases in vehicle excise duty, while Autocar magazine and the AA reckon road tolls will become a major expense.
The SMMT says proposals to charge motorists driving the most-polluting cars - those in band G - £1800 a year in tax will also hit those running far smaller cars.
A suggested £300 difference in costs between each band means motorists driving economical cars such as the Nissan Micra from band B could see tax bills rise from £40 to £300. Combined with projected increases in fuel costs, the SMMT believes the Micra driver will pay £837 for fuel and road tax in 2006, rising to £1181 in 2009.
SMMT Chief executive Christopher Macgowan said: 'Changes to road tax would hit drivers of small and family cars in a tax double-whammy, firstly through fuel costs and secondly road tax. It would add more pain to struggling families.'
Over the next decade, What Car?'s sister magazine Autocar says that over the next decade congestion charges will make variable costs bigger than the fixed costs of tax, insurance, loans and depreciation.
It predicts that the driver of a 1.6-litre Ford Focus will spend around £1000 a year on tolls by 2015, while road tax will jump from £135 to £750.
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