The Climate Change Bill will make the government's target of a 60 per cent reduction in carbon dioxide emissions by 2050 legally binding for the first time.

The Bill also enshrines a target for a 26 to 32 per cent reduction by 2020, and a new system of five year 'carbon budgets' which the government is claiming as a world first.

From next year, three such budgets - representing 15 years - will always be in effect.

The Bill was published in draft form in March, and has been scrutinised by a joint committee of both houses of Parliament.

When the decision was made to publish it in draft form, green campaigners said the delay showed the government was not serious about its flagship legislation. Ministers said it had always planned to put the Bill out for consultation.

'Carbon budgets' were introduced into the legislation to head off criticism from the Conservatives, who were calling for binding annual emission cuts.

The Bill also establishes a new statutory body, the Committee on Climate Change, to provide independent advice and to alert Parliament if the government is not staying within its budgets.

The committee will report annually to MPs, and the government will have to report on its progress at least every five years.

The Bill also gives the government the power to introduce carbon trading schemes without needing to go back to Parliament.