Britain is likely to put forward legislation within three months to cut carbon emissions by at least 60 percent in the fight against global warming, environmentalists said on Wednesday.

The Climate Change Bill is expected to go to parliament in November and could become law by May after parliamentary scrutiny and public consultations on the preliminary draft of the legislation ended this month.

"We expect it after the Queen's Speech in November and to go into committee in December," said Friends of the Earth climate campaigner Mike Childs.

"Because it has already been through pre-legislative scrutiny it could go quite quickly through the parliamentary process and even become law in the spring," he told Reuters.

A spokeswoman for the Department of the Environment would only say the bill was scheduled for the autumn and, depending on the parliamentary timetable, could be law by mid-2008.

The draft bill says carbon dioxide emissions must be cut by at least 60 percent from 1990 levels by 2050 -- and half that by 2020 -- with five-year rolling carbon budgets on the way there and an independent committee to monitor progress.

Environmentalists want annual cut targets -- a goal the government says is impractical -- the inclusion of emissions from maritime transport and aviation, and the final ceiling to be raised to 80 percent from 60.

Three parliamentary committee reports have largely echoed the environmentalists' criticisms, and the government is now considering the reports and public responses to the draft before coming out with the final bill.

"The government's policy towards the 2050 target is clearly incoherent," said the report from the joint committee of both houses of parliament earlier this month.

"The government remains committed to limiting global warming to a rise of two degrees Celsius; but it also acknowledges that, according to recent scientific research, a cut in UK emissions of 60 percent by 2050 is now very unlikely to be consistent with delivering this goal," it added.

Scientists say average global temperatures will rise by between 1.8 and 4.0 degrees Celsius this century due to carbon emissions from burning fossil fuels for power and transport, causing floods, droughts and famines worldwide.

The Climate Change Act will make Britain the first major country to set binding legal limits on its greenhouse gas output.

But environmentalists note that carbon emissions have actually risen since the Labour government came to power in 1997.