The Liberal Democrats named the day today for the end of the petrol-powered motor car as they adopted by far the most ambitious policy to reduce carbon emissions of any major British party.

According to proposals overwhelmingly backed by delegates at the party conference in Brighton, a future Liberal Democrat government would ban petrol cars by 2040 en route to making Britain entirely carbon-neutral by the middle of the century.

"Throughout the world, animal life is hanging by a thread," Environment spokesman Chris Huhne said. "More than a third of all species are likely to become extinct if we do not stop now. It's not just about saving the panda - it's saving human life."

Under the proposals adopted today, which the party hopes will give a boost with green-minded voters, the Liberal Democrats will set a target for 30 per cent of UK electricity supplies to come from non-carbon emitting sources by 2020, rising to 100 per cent by 2050.

Mr Huhne warned delegates that climate change means “far more wild weather” following the devastating floods over the summer and there was little time left to change the way people live.

He said: “We still have to make that leap. We have to summon up the courage. What sort of people are we if we value our own instant pleasure more than our children and their futures on this planet.”

Mr Huhne attacked the Government’s record on the environment, and said of the Prime Minister: “Brown is not green. Never has been and never will be.”

He also turned on the Tories, saying they were pulling in two different directions with John Redwood’s policy group recommending road building and airport expansion, while John Gummer’s report advocated green taxes and carbon reduction.

Mr Huhne said: “David Cameron’s circus skills are going to be tested if he rides these two horses in different directions.”

Focusing on the development of renewable power, the Lib Dems' new climate policy includes scrapping plans for new nuclear power stations.

It also means a sharp increase in Vehicle Excise Duty for gas-guzzling cars, before an eventual ban on petrol-powered vehciles. Mr Huhne said: "The EU Commission wants to set limits on car emissions, but it should state clearly that no car can be sold in the EU if it still belches carbon by 2040. It can be electric. It can be fuelled by a hydrogen cell. But we have to get tough with car-makers about emissions.”

Some of the other key proposals in the Liberal Democrat’s Zero Carbon Britain plan are

:: Creating a future transport fund by charging lorries to use the UK’s roads in order to double rail investment, possibly creating a high speed line running north to south

:: Establishing an international “leapfrog fund” to help developing countries adopt low-carbon technology

:: Boosting spending on flood defences to respond to climate change

:: Encouraging microgeneration by paying a higher rate to producers who export energy to the National Grid

:: Imposing a climate change levy of £10 on domestic flights

The policy did not escape criticism however, including from floor delegate John Allen, who said: “Climate change has always happened and it always will happen, stability is not possible. We might as well propose perpetual motion machines as party policy.”

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