The Government has become the first in the world to commit itself to legally binding reductions in carbon dioxide emissions but will come under strong pressure to agree to bigger cuts when its landmark Climate Change Bill goes though Parliament.

In a draft Bill published yesterday, ministers promised to enshrine into law their commitment to cut emissions by 60 per cent by 2050. Opposition parties and Labour MPs joined forces in calling for an 80 per cent reduction. But even the Government's critics gave the Bill a broad welcome. Hailing a "historic day", Tony Blair said: "This is a revolutionary step in confronting the threat of climate change. It sets an example to the rest of the world but, as important as anything else, it listens and responds to the strong desire on the part of the British people to take the lead and keep it."

The Bill also sets an interim target of reducing emissions by between 26 per cent and 32 per cent by 2020. Legally binding five-year "carbon budgets" will be fixed 15 years ahead to keep it on course.

A new Committee on Climate Change, appointed by the Government, will provide independent expert advice. Although ministers have rejected calls for annual targets, they promised to make an annual progress report to parliament.

David Miliband, the Environment Secretary, said the Bill provided a "robust and durable" framework and expected it to become law by Easter next year. He admitted that ministers would not end up "at the Old Bailey" if the targets were missed but said the Government could face a judicial review. His officials said pressure groups would be able to apply for such a review, allowing judges to "name and shame" the Government or force it to buy more "carbon credits" to permit higher emissions.

The Tories and Liberal Democrats criticised the absence of annual targets but environmental campaigners on the Labour benches said they were unlikely to rebel over that. However, they said they might make common cause with opposition MPs in trying to amend the Bill so that it committed the Government to an 80 per cent cut.

Colin Challen, a Labour MP who is to become a climate change campaigner after the next general election, said the latest evidence pointed to the need to go further than 60 per cent. "The Bill is excellent but we need to have a higher emissions cut by 2050. We have got to aim high," he said, adding that 90 per cent might be required.

Peter Ainsworth, the shadow Environment Secretary, welcomed the measure but said that the Tories' policy review might conclude that an 80 per cent cut was needed. "There are areas where the Bill will need toughening up," he said.

Chris Huhne, the environment spokesman for the Liberal Democrats, said: "The science is suggesting that we have to go higher than 60 per cent, probably around 80 per cent." He criticised the delay in introducing a full Bill rather than a draft, warning that Gordon Brown, if he becomes Prime Minister, might try to water down a measure to which Mr Blair was more committed. The Tories and Liberal Democrats expressed concern about the five-year targets period, saying that one government could try to pin the blame for missing them on its successor.

Sian Berry, principal speaker for the Green Party, said: "A target of 60 per cent by 2050 is not nearly enough - we need to achieve 90 per cent cuts by this date. Scientists say that anything less makes it probable that global temperatures will rise by more than 2C, which will have disastrous consequences."

The draft Bill marks a victory for pressure groups who have fought a long campaign for legally binding targets. Tony Juniper, director of Friends of the Earth, said: "We are delighted the Government has recognised the need for a new law to tackle climate change. But the draft Bill must be strengthened if the UK is to set a global example. It must include bigger cuts in carbon dioxide emissions and make all future governments accountable for their role in delivering these cuts."

Arnold Schwarzenegger, Governor of California, hailed Mr Blair as an "action hero" for inspiring him to introduce a law committing California to an 80 per cent reduction in CO2 emissions by 2050. In a joint interview with Mr Blair for ITV News, Mr Schwarzenegger said: "It is very clearthe Prime Minister has been a great inspiration to many, many countries all over the world... I think he is a pioneer, because he has had the guts to sign the Kyoto treaty and to show to the world that you can protect the environment and protect the economy at the same time."

The Climate Change Bill's main points

* Britain is to become the first country in the world to set legally binding targets for cutting its carbon dioxide emissions. The targets will be aimed at cutting emissions of the gas which causes global warming by between 26 per cent and 32 per cent by 2020, and 60 per cent by 2050.

* New system of five-year "carbon budgets" to cap total emissions. Limits set 15 years in advance to help business planning. Ministers say that the caps will set a "trajectory" for hitting longer term Government CO2 emissions targets.

* Courts are to be given powers to "name and shame" ministers if targets are missed.

* An Independent Committee on Climate Change will be established to advise on progress towards hitting emissions targets.

* The committee will be tasked with making annual reports to Parliament on progress towards emissions targets.

* Ministers required to produce five-year reports on the potential impact of climate change and their responses.

* Government will be granted new powers to introduce regulations to help ministers impose future controls on emissions, such as a possible future domestic emissions trading scheme.

(By Andrew Grice, The Independent, 14/03/2007)