Six of the UK's ten nuclear stations are not operating at full capacity. Three are completely closed, one is operating at half capacity and two have been reduced to 70 per cent because of safety fears.

British Energy says Dungeness, in Kent, which is shut for maintenance, Heysham 1, in Lancashire, and Hartlepool, in County Durham, should be partially operational by the end of the year.

But some analysts fear this could leave the country short of energy next month.

Jeremy Nicholson, director of the Energy Intensive Users Group, said: "In ordinary circumstances, nuclear would be running flat-out during the winter. That's the whole point of it – to supply base load.

We are all crossing our fingers, but I can't say we are too optimistic."

National Grid forecasts indicate low energy surpluses in November, but a spokesman said: "There's nothing we've seen to indicate power cuts."