THE cost to the taxpayer of making Britain's nuclear power stations safe has soared to nearly Pounds 70billion, it emerged last night.

Funding the cleanup of nuclear waste and decommissioning 20 civilian sites including Sellafield in Cumbria and Dounreay in Caithness, northern Scotland will cost far more than the original Pounds 48billion estimate.

The figure could be higher still because officials admitted they will not know the 'full costs' until 2008.

And if the Government decided to reclassify plutonium as waste rather than as an asset, the costs would be pushed up by another Pounds 10billion.

The massive burden on the taxpayer was revealed as ministers confirmed the sale of British Nuclear Group, which will hand over control of Sellafield to the private sector.

The original Pounds 48billion estimate for cleanup and decommissioning was increased to Pounds 56billion last year in a report by the Nuclear Decommissioning Authority.

But yesterday the authority said the estimate of costs had risen again, to Pounds 63billion, and the potential need for a further Pounds 7.5billion had also been identified.

Officials insisted the new figure was because of speeding up the decommissioning of 1950s stations. Tony Blair is planning to give the go-ahead for a new era of nuclear energy stations later this year in an effort to tackle the problem of Britain's dwindling gas supplies.

The Government's Trade and Industry Secretary, Alan Johnson, said he believes a competitive sale is in the best commercial interests of the group's parent company, British Nuclear Fuels.

He added: 'By bringing in external expertise more quickly, it also contributes to improved cleanup performance for the NDA and is therefore good for the taxpayer.' The decades-old facilities are suffering-widespread damage which could pose a deadly risk to humans and wildlife. In one incident in 2004, thousands of gallons of highly radioactive spent uranium and plutonium enough for 20 nuclear bombs leaked unnoticed for months at Sellafield's Thorp reprocessing plant.

It was the most serious nuclear waste leak anywhere in the world in 2004.

The incident was blamed on a faulty pipe which had been hit by metal fatigue.

Sellafield and Dounreay are both classed as 'high hazard' because of the high volume of radioactive waste to be disposed of.

BNFL's chief executive Michael Parker said the sale of the cleanup business is a 'positive strategic move' for the business and workers.

Lawrie Haynes, British Nuclear Group's chief executive, said: 'A strong British Nuclear Group means strong competition and that can only be good news for the NDA and the UK taxpayer.' But Friends of the Earth director Tony Juniper said: 'UK taxpayers will have to pay the spiralling bill of dealing with Britain's dangerous nuclear legacy, which could now be as high as Pounds 70billion.

'Nuclear waste stays highly radioactive for many thousands of years, and we still don't know how to safeguard it for the future. The announcement demonstrates the economic and environmental insanity of nuclear power.' The Conservatives are particularly unhappy with the timing of the news.

Shadow trade and industry secretary Alan Duncan said: 'Making this statement on the day the House rises for Easter is typical of Labour's sneaky practices. The announcement is being made in the middle of the Government's Energy Review, in which the crucial question of how the nuclear sector might work with Government is being examined.

'Gordon Brown did not mention the disposal of British Nuclear Group in the Budget statement last week.

'To dump 50 years of dubious waste on to the private sector with none of the guarantees that only Government can offer needs serious public debate.'

j.merrick@dailymail.co.uk