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 Times has learnt.

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. The policy document, Zero Carbon Britain, claims the Liberal Democrats would ensure that Britain was carbon-neutral by 2050.

It says: “It is clear that the Labour Government’s aim of a 60 per cent cut in carbon-dioxide emissions by 2050 will not be enough. A reduction in emissions of the magnitude that we are advocating will only happen if developed countries such as the UK take the lead by cutting their emissions. The objective of climate change strategy must be to make the UK carbon-neutral over the longer term.”

The party is determined to make the environment a key theme next month and has pledged to bring together environment, energy and transport together into one Cabinet brief if it were to win power.

The policy paper also suggests restricting Britain’s runway capacity to current levels and introducing new pollution taxes covering passenger and freight flights as part of a package to try to restrict the future expansion of air travel.

The party reaffirmed its opposition to the Government’s Aviation White Paper, which the policy group says encourages expansion of large airports. They say that emissions from air travel are set to rise by 83 per cent on 2002 levels by 2020, and that they could amount to about a quarter of the UK’s total contribution to global warming by 2038.

The Lib Dems would charge a climate change levy on domestic flights, as well as replacing the Airport Passenger Duty with the pollution charge on flights to all destinations.

The party proposes that, by 2040, all new cars must emit zero carbon, while all freight must be running on electricity, biofuels or other renewables by 2050. It is also proposing introducing high-speed rail lines, and wants to turn the Government’s climate change levy into a carbon tax that would apply to primary fuels.

The Lib Dems want 30 per cent of the UK’s electricity to come from clean, non carbon emitting sources by 2020, rising to 100 per cent by 2050, providing new incentives for renewable sources and small-scale micro-generation with guaranteed prices. It rejects the Government’s plan to introduce a new generation of nuclear power stations.

The policy document also says that Britain must reach agreement on a much more ambitious set of targets in the negotiations for the successor to the Kyoto Protocol, allowing a “multi-stage” approach depending on national circumstance.

It also thinks that the EU emissions trading scheme should be strengthened, linking it to the EU target to reduce greenhouse gas emissions and broadening the scheme to cover aviation, shopping and road transport through fuel suppliers.

The proposals

— Ensure Britain produces zero carbon emissions by 2050

— Strengthen emissions trading scheme

— Tighten building and planning standards

— Graduated car tax up to £2,000 and emissions charge per aircraft rather than passenger duty

— Lorry road pricing on motorways by distance and emissions

— High-speed rail line

— Zero-emission homes from 2011 Introduce “green mortgages” to fund the upgrading of housing stock Cut half of emissions through use of waste products for energy generation

— Climate change levy on domestic flights

— Limit runway capacity to current levels

— All new cars must be zero carbon from 2040

Source: Liberal Democrats