Green groups have said Treasury plans to impose a floor price on carbon used in electricity generation amounts to giving billions of pounds to the nuclear industry – something the coalition government said it would not do.
They said that it was a secret way of subsidising the nuclear industry, which could benefit by up to £3.4 billion.
The Treasury's consultation on the “carbon price floor" closed at the end of last week.
Greenpeace and WWF said this would breach the coalition's agreement not to subsidise nuclear power.
The £3.4 billion figure is based on a minimum carbon price of £40 per tonne. However, sources suggest it is more likely to be lower, perhaps half that figure. Nevertheless the resultant amount going to the nuclear industry, of £1.7 billion, which would be over 13 years, is still a considerable amount.
These figures are based on the existing amount of nuclear capacity and do not take into account any new nuclear plants, which would increase the amount.
WWF and Greenpeace are calling for a windfall tax on existing nuclear generators alongside the carbon floor price mechanism, that would be used to support energy efficiency and emerging renewable technologies through the Green Investment Bank.
They have issued scenarios which describe how the world could power itself by up to 95% renewable energy by 2050, and regard nuclear power as unnecessarily risky and harmful.
Dr Douglas Parr, Chief Scientific Adviser and Policy Director, Greenpeace UK said: “This is yet another taxpayer handout to a failing nuclear industry. The economics of nuclear power have never added up and it has been continually propped up with money from hard-working families."
The eventual policy is to be determined in concert with the ongoing Electricity Market Reform (EMR) consultation.