Nuclear power should supply around 30% of Britain's energy needs, tackling the impact of climate change, Tony Blair's chief scientific adviser suggests.
Mr Blair has raised the prospect of new nuclear power stations
Sir David King said as many as 20 new nuclear plants could be needed to increase the power generated by the current 12 sites from the current 12%.
Combined with more renewable energy, this would cut fossil fuel use, he told BBC One's Sunday AM.
The prime minister recently signalled his support for the nuclear option.
Mr Blair told the CBI annual dinner this month the issue was "back on the agenda with a vengeance".
Sir David said he did not believe a final decision on the UK's nuclear future would be made before the publication of the government's energy review, due in July, and the report of the Stern Commission on climate change.
But he said any new nuclear power stations would not be funded through new taxes, insisting instead that the money markets would have to decide if they want to invest in them.
He added that new technologies - such as using bioethenol (virtually carbon free) and hybrid cars in the future as well as nuclear power - would allow consumers to continue the current extent of car and plane use.
Sir David said no decision is expected before the energy review.
"We can all live at the same comfort levels but looking at different energy sources and better energy efficiency," he said.
Asked what proportion of Britain's energy needs should be supplied by nuclear power, Sir David said: "My favoured figure is around 30%.
"We would then have baseline energy through the year from nuclear plus renewables and we can then diminish our dependence on fossil fuels."
Jonathan Porritt, the chairman of the Sustainable Development Commission which advises the government on environmentally-friendly growth, accepted policy-makers had to consider whether nuclear power should play a part in Britain's energy future.
But he said the potential reductions in CO2 emissions which could be gained from switching to atomic power came to only around 8% of Britain's output - far less than could be saved by simply using current energy supplies more efficiently.
'No hair-shirt future'
"If the prime minister wants to make nuclear power the test of his leadership on climate change here in the UK, he is genuinely deluded," Mr Porritt told Sunday AM.
The role of government was to "fashion the markets" to make the choice for consumers easier, he said.
It need not be "the end of life as we know it", he said, but may mean people making short journeys on foot or bike and paying for the carbon cost as well as the travel costs for foreign holidays.
Sir David suggested Mr Blair should put more pressure on the US - the world's biggest producer of greenhouse gases - to change its patterns of energy use.
Effective action on climate change "means talking tough even to your friends," he said. "It means explaining to your friends that leadership is required other than from Britain on this issue."
Sir David said he believed Britain would be able to cut its own greenhouse gas emissions without resigning itself to a "hair-shirt future".