A leading Green Party campaigner in Oxford has sparked controversy after claiming new nuclear power stations could cut carbon emissions.

Until recently, Mark Lynas, the author of the award-winning Six Degrees: Our Future on a Hotter Planet – which predicted that Oxfordshire could be hit by 40C summers and winters of flash flooding in 30 years’ time, if global warming was not slowed – opposed increasing nuclear power, along with many Green Party members.

But the Wolvercote environmentalist has caused a stir, along with three colleagues in the party, by changing his stance on atomic energy.

The 35-year-old father-of-two admitted that switching to the Government’s line on nuclear power was, for environmentalists: “A bit like admitting you are gay to your parents.”

Mr Lynas said: “Some of the predictions in the early chapters of my book have already happened and we are experiencing climate change on an accelerated scale.

“If you rule nuclear power out of the mix, it makes it impossible to close all the coal-fired power stations, like the one at Didcot.

“Coal-fired power stations emit millions of tonnes of carbon dioxide a year, which is one of the principal causes of global warming.”

Green city councillor Sushila Dhall said: “Mark’s views are not representative of the Green Party in Oxford, which is concerned about the potential problems of finding suitable places to bury radioactive nuclear waste.

“We should focus instead on home insulation and renewable energy.”

But Mr Lynas, who is secretary of the Upper Wolvercote Allotments Association, said: “I’ve been equivocating over this for many years. It’s not as if it’s a sudden conversion, but it’s taken a long time to ‘come out of the closet’.

“The thing that initially pushed me was seeing how long and difficult the road to going to a 100 per cent renewable economy would be, and realising that if we are really serious about tackling global warming in the next decade or two then we certainly need to consider a new generation of nuclear power stations.”

In 2007, a report compiled by leading energy analyst Ian Jackson cited Didcot power station and Harwell, the former headquarters of the UK civil nuclear research programme, as possible sites for new nuclear power stations.

But Mr Lynas said he thought it “unlikely” new nuclear plants would be constructed in Oxfordshire, with existing nuclear sites the likely option for the next generation of nuclear power stations.

The Government is seeking public support in the selection of the sites where new nuclear plants will be built by 2025.

Other leading environmentalists who have changed their stance on the nuclear issue include Oxford-based Green Party activist Chris Goodall, Stephen Tindale, former director of Greenpeace, and Lord Chris Smith, chairman of the Environment Agency.

Mr Goodall said: “We not jumping up and down saying ‘wouldn’t it be great if there was a nuclear reactor at Didcot’, but we feel the nuclear option has to be kept open.”

City council Green group leader Craig Simmons said: “Yes, nuclear power will plug an energy gap, but there are lots of questions about the feasibility of delivering it.”