"Blair seems to have fallen for the nuclear industry's propaganda campaign," Friends of the Earth director Tony Juniper told Reuters. "But it is the wrong decision. Nuclear is unsafe, the technology untested and in any case far too expensive."

All but one of Britain's nuclear stations will close by 2023. Without new ones, nuclear power will provide four percent of Britain's electricity by 2010, down from 21 percent now.

The government is being driven by the Kyoto treaty to cut carbon dioxide emissions by 12.5 percent below 1990 levels over the next seven years. It classifies nuclear as emission free.

The Campaign for Nuclear Disarmanent disputes this, saying extraction and refining of uranium produce carbon emissions. "It is not the answer to Britain's energy needs and is not a solution to global warming," it said.

Although Blair's office has denied that he has taken any decision, a government source told Reuters he had become a nuclear convert but the cabinet was divided on the issue.

The key lies with the Treasury which would have to approve the huge government subsidies, in capital investment or guaranteed prices, and finance minister Gordon Brown.

He is expected to take over from Blair before the next election, due in 2010 at the latest. Brown has not made any recent public statements about his views on nuclear power.

NO PUBLIC MONEY

Pressure to review the country's energy policy is coming from the convergence of several factors: booming oil prices, global warming caused by burning fossil fuels, an increased emphasis on the security of energy supply and the need to decide soon about whether to replace existing nuclear plants.

The government insisted on Wednesday that if the decision were taken to go nuclear it would not involve any public money.

"There is no expectation of taxpayers' money being thrown into this ... It's down to the private sector," Trade and Industry Secretary Alan Johnson told a parliamentary committee.

But potential investors have made it clear they will not commit the money without some form of government guarantees.

Juniper said new nuclear plants would only cut greenhouse gas emissions by 8 percent because electricity generation accounted for only a third of carbon dioxide output -- with much of the remainder coming from road and air transport.

"Energy efficiency and renewables together could have a far bigger impact," he said.

Environment Agency Chairman John Harman expressed doubts about the economics while environmentalists said there was no guaranteed method of dealing safely with deadly nuclear waste.

"I still don't believe the rise in fuel costs is enough to float nuclear off the economic rocks," he told Reuters.

Officials say Blair will announce within two weeks a full-scale review of Britain's future energy needs to be completed in 2006, after which a final decision will be taken.

"It is unsafe, uneconomic and unnecessary," Andrew Lee, head of campaigns at conservation group WWF, told Reuters.

"From our point of view, there is no surer way of killing off renewables than opting for nuclear."