The UK is to work towards radical cuts in greenhouse gases - a reduction of 60% on 1990 levels by 2050.
It aims to achieve this through more efficient energy use and greater dependence on renewable sources like wind power.
It plans to build no new nuclear power stations to replace the present generation.
The proposals have been fiercely contested between different government departments.
They are spelt out in the Energy White Paper, to be published on 24 February (Monday), which is the official response to a report on climate change by the Royal Commission on Environmental Pollution (RCEP) in 2000.
The nuclear option has been decisively kicked into touch
That urged a 60% cut in carbon dioxide (CO2), the main greenhouse gas caused by human activities, by mid-century to avoid massive climate change.
After protracted wrangling between the Treasury, the environment department, and the Department of Trade and Industry, the White Paper is expected to chart a radical course towards a low-carbon economy.
It is likely to say:
- developed countries, including the UK, should work for 60% carbon cuts by 2050
- the UK should do this by reducing demand for energy through improving the efficiency of its use (the amount of energy wasted is put at £5 billion annually)
renewable energy use should be expanded
The White Paper will probably say coal is still important for generating power.
Devil in the detail
There will be more research into ways of storing CO2 where it cannot affect the climate, probably deep underground.
Sceptics expect ministers will almost certainly leave some options open
Some environmental groups say the White Paper vindicates their years of campaigning.
Bryony Worthington, of Friends of the Earth, told BBC News Online: "Politically this is quite a significant announcement. The nuclear option has been decisively kicked into touch."
But sceptics say the devil is in the detail, expecting ministers will almost certainly leave some options open.
A comprehensive review of energy policy is expected in about 2005, for a start.
And on nuclear power the government will probably say it cannot rule out a possible need one day for a new generation of power plants.
One energy analyst told BBC News Online the document would be too vague to raise real hopes.
"It'll be light on actual targets", he said.
"It will speak much more of 'aspirations' or 'goals'. The government is backing away from targets wherever possible - that way it thinks it can't be held to account. The White Paper will be a fudge."
'RENEWABLE' ELECTRICTY TARGETS
Current target: 10% of electricity to come from renewables by 2010
Likely new target: 20% renewable electricity by 2020
But while ministers may rule little out, they do appear to have ruled in an unambiguous commitment to renewable energy, to the sceptics' surprise.
The government's present target is for 10% of electricity to come from renewables by 2010.
Late drafts of the White Paper contained no firm commitment to improve on this, probably because of Treasury objections.
But a source who has seen the version to be published has told the BBC it is expected to set a new target (though it may avoid the word itself) - 20% renewable electricity by 2020.
The White Paper will not tackle aircraft carbon emissions, which are not controlled by international agreement and are a rapidly rising proportion of total emissions.
The government wants to focus on renewable energy instead
It is unlikely to say anything much about land transport, which in the UK will soon emit more CO2 than electricity generation.
But it will offer a way forward in a world of growing competition for oil and gas.
By 2010 the UK is on course to be a net fuel importer, for the first time since the industrial revolution.