The Government is facing a back-bench tax revolt over plans to increase Vehicle Excise Duty for more-polluting cars in 2009.
Ronnie Campbell, MP for Blyth Valley in Northumberland, has tabled a motion calling for the tax to be scrapped, and 20 MPs have backed him.
Although the proposals are not due to come into effect until April, he fears the VED rises could become a festering political issue.
In March's Budget, Chancellor of the Exchequer Alistair Darling announced plans to increase VED on the most-polluting vehicles from April next year, and cut rates for cleaner cars.
However, the plans, which will raise an extra £735 million in tax for the Government during 2010-11, will increase VED costs for many older vehicles registered since 2001, including popular family cars such as the Ford Focus and Renault Megane.
A Treasury spokesman defended the measures, saying the reforms to VED are aimed at ensuring that people gain financially by choosing cars that pollute least.
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