The Liberal Democrats have declared war on fuel-guzzling 4x4s, dubbing them "Chelsea tractors".
The Lib Dems say 4x4s use too much fuel
The party has pledged to tax the people carriers off the road, claiming they are dangerous and environmentally unfriendly.
Party chairman Matthew Taylor said it was wrong to tell people what type of car they should drive.
But the party would instead use incentives to persuade them to choose more fuel efficient cars, he said.
He told the party's conference in Bournemouth: "If you drive a huge American people carrier or four-wheel drive you are going to pay more than if you drive a small fuel-efficient family car.
"I think Chelsea tractors can expect to pay more. They are not environmental. They use more fuel. They are also extremely dangerous to pedestrians."
He said ordinary family saloons were designed "so you will ride off over the bonnet" in the event of an accident, but "if you are hit by a 4x4 you are normally caught under the vehicle".
Lib Dem campaigns chief Lord Razzall said public pressure would also help persuade motorists to abandon their 4x4s.
"Individual freedom means they can carry on driving them until a campaign embarrasses them into not doing it," he said.
"That is what tends to happen. A few kids get killed around a school and people soon think `Oh my God, do I want to drive to school in that'?"
The Lib Dems say they wanted to use the tax as a tool to make people more environmentally-friendly rather than to raise cash.
The party also wants to use tax cuts as an incentive to boost recycling and cut pollution.
It also want to reward businesses and individuals who take care of the environment.
Among a range of incentives to cut pollution, delegates agreed households producing less non-recyclable waste should get tax breaks.
Environment spokesman Norman Baker said waste and pollution cost Britain £67bn a year.
"The polluter must not pay the taxpayer," he said, adding: "We believe in taxing differently, not more."
That meant offsetting "green" charges with other tax cuts.
Tony Blair gave a major speech on climate change last week but Mr Baker said the prime minister had to go beyond "ritual" speeches made once a year.
"Climate change is a weapon of mass destruction and far more real than the ones you've been vainly combing Iraq for," he said in his attack on the prime minister.
Former Friends of the Earth chief Jonathon Porritt, now a government environmental adviser, said government had not done enough to get citizens help produce a sustainable future.
Praising the Lib Dem contribution, Mr Porritt told the conference: "Given the historical record of the Lib Dems you may well claim that you're
far better placed to carry through that kind of crusade than any other party in
"I couldn't possibly comment on that."