Conservative leader David Cameron is to commit his party to reducing carbon emissions from cars by nearly a third.
The Lib Dems have accused Mr Cameron of 'global posturing'
He will outline a series of incentives to get people to switch to more environmentally friendly cars.
He also wants more school buses to cut down on parents unnecessarily using their cars on the school run.
Labour has accused Mr Cameron of "flip-flopping" on green issues and of using "platitudes" after he said he wanted a "green revolution".
Mr Cameron's emissions target would mean virtually all cars on Britain's roads would have to be powered by new technologies such as hybrid motors.
He has declined to say whether he would increase vehicle excise duty for gas-guzzlers or impose a green tax on air flights which produce high levels of greenhouse gases.
He has also indicated he is against a ban on road-building.
But senior Tory sources say "ideas are coming" to deal with the school run in particular.
Mr Cameron has made "vote blue, go green" the party's slogan for the elections, which take place on 4 May, but he continues to face criticism that he lacks concrete policies.
The Green Party said "the proof is in the pudding" challenging the Conservative leader to stop his councillors pursuing the "traditional Tory agenda of privatise and pollute".
Speaking on BBC1's Breakfast, Mr Cameron said that people who drive cars which are more environmentally friendly will pay less tax, although he stopped short of making a policy announcement.
He said he wants emissions cut from 170 grammes per kilometre now to 100g for new cars by 2022 and all cars by 2030.
He has swapped his Vauxhall Omega for a Lexus with a hybrid engine (emissions 184g per KM). Critics say he could have got a cleaner Toyota Prius (104g).
He hit back claiming a Prius could only fit four people in it and in his job he often needed more space than that but he said by getting rid of his government-provided car, the Omega, he had got rid of a "real gas guzzler".
"What I am saying is we have to do something about global warming," he told the BBC adding that transport was responsible for 20% of greenhouse gas emissions in the UK.
But that prompted Lib Dem environment spokesman Chris Huhne to accuse Mr Cameron of "more empty gesture politics".
"To suggest that a Prius is not adequate for a senior politician is utter nonsense. Sir Menzies Campbell received a tour around my constituency in my Prius only this morning. If it is good enough for Menzies Campbell, then it is good enough for David Cameron."
The Tory leader has also pledged to put Britain at the forefront of international efforts to build a new generation of motor vehicles that are much less environmentally damaging,
In the March Budget Chancellor Gordon Brown announced a zero-rate road tax for low-emission cars but none of the models that would be eligible are currently on sale in the UK.