Prime Minister Tony Blair should "give the green light" to a new generation of nuclear reactors, his chief scientific adviser said. Mr Blair faces stiff opposition from green groups and some in his Labour Party if he sanctions new reactors.

But Sir David King said faced with the reality of global warming, "the equation is simple".

Nuclear power met almost a quarter of Britain's energy needs in recent years but that will fall to just 4% by 2010 if reactors are not replaced. "All of that is coming from a CO2 free source. I think we need every tool in the bag to tackle this problem,"

Sir David told BBC1's Sunday AM programme. The decline in nuclear power was contributing to failure to meet the Government's targets on reducing carbon dioxide emissions by 2010, Sir David said. "We have to take decisions very quickly. I think the important thing here is give the green light to the private sector and the utilities and give them nuclear as an option."