Britain's oil and gas from the North Sea are dwindling and it is keenly aware that Russia, which supplies around 25 percent of the European Union's gas, disrupted supplies last year. It also wants to meet its carbon emission cut targets.

"If nuclear is excluded, there is every chance that its place would be taken by gas and coal generation, which of course emits carbon," Trade and Industry Secretary Alistair Darling told parliament, announcing the Energy White Paper.

"I am quite clear in my mind that it is important that we have a mix of energy supply ... that we don't become overly dependent on imported gas," he added.

Wednesday's white paper follows repeated energy policy reviews over the last few years and concern is mounting Britain will face a power shortage unless decisive action is taken soon.

"Time is against us if we are to avoid power shortages," CBI Director General Richard Lambert said. "The White Paper suggests the government understands what is needed to avoid this energy crunch. The real test now will be delivering these proposals."

Following the report's publication, oil company BP withdrew from bidding to build a UK carbon capture and storage plant -- an unproven technology that buries greenhouse gases and is seen as critical in the fight against climate change.

The government said on Wednesday it would launch a competition for a grant award in November, having previously announced the competition in March.

"That's an extension too far," a BP spokesman said.

As well as securing supplies, Darling said the new measures would save up to 33 million tonnes of carbon by 2020, equivalent to the emissions from every road vehicle in the country.

The government wants to boost energy efficiency and change lifestyles, to cut rising energy demand and carbon emissions.

The European Union aims to get 20 percent of its energy from renewable sources by 2020, and a draft law going through the British parliament calls for the country to cut emissions of climate-warming carbon dioxide by 60 percent by 2050.

NEW NUCLEAR GENERATION

Prime Minister Tony Blair insists Britain needs a new generation of nuclear power plants to replace the 20 percent of electric power the old ones provide.

But because a judge criticised the government earlier this year for failing to consult the public adequately on the nuclear issue, Darling was also on Wednesday forced to launch a 20-week full consultation process.

"The Government's endorsement of expanding nuclear power is the definition of irrational policy. Like a stool with no legs, it fails on economic, energy and environmental grounds," said Andrew Simms of the New Economics Foundation.

Environmental group Greenpeace, which filed the legal challenge, accused the government of tinkering with a failing energy efficiency and renewables policy "while indulging its nuclear obsession".

It said it would not hesitate to go back to court if the government did not consult fairly.

French power giant EDF welcomed the White Paper and said it and the world's largest maker of nuclear reactors, Areva, would ask British authorities to certify the latest "EPR" reactor.

The clock is ticking. All but one of the existing nuclear power plants are scheduled to close by 2023 and even the most optimistic pro-nuclear lobbyists reckon it will take a minimum of 10 years to build a new plant from scratch.

Darling said a decision on new nuclear must be taken this year. He said no public money would go into new nuclear plants.

There is no clear evidence that private sector finance will be on offer for an industry that needs huge initial investment, even if it can later generate power at relatively low cost.