Professor James Lovelock, the scientist and celebrated green campaigner, had opposed any expansion but now believes there is not enough time for renewable energy to replace coal, gas and oil-fired power stations, whose waste gas, carbon dioxide, causes global warming.

Mr Wilson maintained Professor Lovelock's endorsement of the nuclear option was the logical place to be. He has consistently championed a combination of renewable and nuclear energy and argued to keep the nuclear option open in the government's energy paper.

He said: "I have long argued that at some point the environmental movement would have to confront the real choice - are they more against nuclear power than they are in favour of taking global warming very, very seriously?

"Professor Lovelock has had the courage to address the question honestly. I hope many others will follow him in questioning the basis of their hostility to nuclear power."

Professor Lovelock pleaded with his friends in the green movement to drop their objection to nuclear energy. He said: "Even if they were right about its dangers, and they are not, its world-wide use as our main source of energy would pose an insignificant threat compared with the dangers of intolerable lethal heatwaves and sea levels rising to drown every coastal city in the world."