The Liberal Democrats would raise taxes on the most polluting cars to up to £2,000 a year as part of a package of measures designed to combat global warming.

The tenfold increase in vehicle excise duty for the worst offending cars would provide a “real incentive” for consumers to switch to more environmentally-friendly cars, the party’s climate change group has said.

The Lib Dems propose that zero carbon vehicles should pay no road tax, and claim their plans would ensure that road transport emits no carbon by 2050.

The policy is part of a series of measures to be presented during party conference in an attempt to regain the initiative on the environment from the Conservatives. It is likely to be adopted as party policy after a vote at next month’s conference in Brighton.