Paul Tyler, the party's transport spokesman, will set out a commitment for reducing car use by introducing duty at different rates and increasing the duty on petrol.
The Liberal Democrats believe the move will be popular with the public, who are becoming increasingly concerned about the effect of vehicle emissions on health.
The Chancellor raised duty for all cars by pounds 5 to pounds 135, roughly equivalent to the inflation rate, in the Budget last November but he has rejected demands for it be levelled according to engine size.
The Liberal Democrats will propose that duty should be reduced for those using fuel-efficient cars, with a banding system of higher charges for larger, less fuel-efficient cars.
The aim would be to encourage people to switch to smaller vehicles and the cuts in revenue would be balanced by an increase in petrol duty. The Treasury has tried to encourage wider use of unleaded petrol through higher rates of duty on leaded fuels but the differential has been narrowed.
The Liberal Democrats would enforce tougher control measures, making the MoT emissions test more rigorous, and encourage the use of low-sulphur fuel, and ensure the fitting of catalytic converters and particulate filters to older vehicles.
They would also switch investment away from road building to public transport and would enable local authorities to introduce urban road pricing to force motorists to pay for driving into cities and towns in peak hours.
tLord De Ramsey, the chairman of a family company farming 6,500 acres in Cam- bridgeshire and a former president of the Country Landowners Association, was yesterday appointed chairman of the Environment Agency.
The agency takes over the work of the National Rivers Authority, HM Inspectorate of Pollution and the London Waste Regulation Agency next April.Reuse content