The bill sets a target of cutting national emissions of climate-warming carbon dioxide by 60 percent by 2050 and about half that by 2025. It would make Britain the first country to adopt such a legally-binding commitment.
"I expect the Bill to be published to parliament on Thursday," a government source said on Tuesday on condition of anonymity. The legislation will be fast-tracked.
Over the past six months of pre-legislative parliamentary scrutiny of, and public consultation on, the Climate Bill environmentalists and many politicians have campaigned for an 80 percent carbon dioxide cut goal and annual targets on the way.
The government has rejected binding annual carbon cut targets in favour of rolling five-year "carbon budgets" and has until recently ruled out raising the end goal above 60 percent.
But Environment Secretary Hilary Benn said last month he would ask a climate monitoring committee to be set up by the bill to see if 80 percent was necessary or feasible.
Scientists say global average temperatures will rise by between 1.8 and 4.0 degrees Celsius (3.2 and 7.2 degrees Fahrenheit) by the end of the century due to burning fossil fuels for power and transport. This will cause floods, droughts, and storms, and threaten millions of lives.
Environmentalists also note that while Britain is on track to meet its Kyoto Protocol commitment to cut carbon emissions by 12.5 percent from 1990 levels by 2012, that is more due to the decline of its smokestack industries than good planning.
They note the country's carbon emissions have risen steadily since the country's Labour government took power in 1997. United Nation's environment ministers will meet on the Indonesian island of Bali early next month to try to agree to negotiate a successor to Kyoto which is the only international carbon-curbing treaty but which expires in 2012.
The goal is to get a deal within two years, giving three more years for ratification by enough nations to make it come into effect -- half the time it took to negotiate and ratify the original treaty. (Reporting by Jeremy Lovell; editing by Robert Woodward)
