The government's chief scientific adviser has warned that ministers will have to take a decision within five years on whether to build new nuclear power stations.

Sir David King said the decision had to be made if Britain is to reach its targets for cutting greenhouse gases.

He told the annual conference of the Chartered Institute of Building Services Engineers: "The government is saying we will come back and look at that when we've seen how well we are doing on energy efficiency gains and renewables. But the timescale to do that is relatively short. I do think five years or less is when we've got to make a decision."