Conservative leader David Cameron has joined environmental campaigners in calling for a law on climate change to be promised in the next Queen's speech.
Mr Cameron has stated a policy of 'binding' emission targets
In a letter to Tony Blair, green groups are pressing for legislation that would set targets for 3% annual cuts in greenhouse gases across the UK economy.
Friends of the Earth say the measure should have cross-party support and the Lib Dems have also signed the letter.
The government says the important point is how to meet existing targets.
Mr Cameron's move comes a day after a demonstration at Britain's largest coal-fired power station, Drax, in North Yorkshire.
'Day of action'
The UK is unlikely to meet its target of reducing CO2 emissions by 20% by 2010, but could reach a cut of 15-18% by then, said a government report earlier this year.
The government set the goal of cutting carbon dioxide emissions by 20% from 1990 levels by 2010 when it came to power in 1997.
At a news conference in Devon with Friends of the Earth director Tony Juniper, Mr Cameron said climate change was the biggest challenge facing the world and politicians had to work together.
Binding targets on cutting carbon emissions every year from now until 2050 would take that issue out of politics he argued.
"Then you can really ask politicians what are you going to do to achieve those targets," he said.
Mr Cameron said the bill would also set up a carbon audit office, with experts advising on progress on meeting the targets.
"Tony Blair often talks about wanting to have a legacy, he's introduced dozens of Bills, hundreds of Bills since being prime minister, many of them already forgotten," added Mr Cameron.
"This would be a bill that will be remembered long after he's gone, long after I've gone."
Just in time?
Mr Juniper said 380 MPs were backing the calls for the climate change bill.
"It's about setting out a framework that can help the country to do what's necessary to reduce emissions that are causing global warming, and to do it on a timescale that's going to avoid the worst effects of climate change," he said.
Carbon emissions from Drax prompted a 'mass' protest
"We still have time - just about - to do this, but we need to act immediately."
Friends of the Earth says it is endorsing Mr Cameron's stance as it was the same as theirs.
The Lib Dem environment spokesman, Chris Huhne, said a climate change bill would be useful.
"It would set a legally binding target forcing both the Tory and Labour parties to come forward with concrete measures to reduce harmful emissions, as the Liberal Democrats have done," he said.
Environment Secretary David Miliband said the government was taking action at home and abroad against global warming.
"We welcome a wider debate on how we can make further progress but we need to focus on the means of achieving it, not on setting additional targets," he said.
Mr Miliband said the UK would be cutting its allocation for the second part of the European Union's emissions trading scheme by eight million tonnes of carbon a year from 2008.
"The recent energy review set out ambitious proposals to get us on course to achieve real progress in emissions reductions and will deliver 19 to 25 million tonnes of carbon savings by 2020," added Mr Miliband.