A row over the future of nuclear energy is threatening to turn into the first major policy debate of Labour's third term.

Leaks in the Sunday Telegraph newspaper suggested that environment and rural affairs secretary Margaret Beckett is "blocking" plans to build new nuclear power stations because of environmental concerns.

A document from the Department of Productivity, Energy and Industry's (DPEI) director general Joan MacNaughton claims that Beckett's position could "damage business competitiveness and [electricity] security of supply".

The government has been reviewing future power options but the leak says is has not been able to consider all the alternatives so far.

"Because Beckett opposes nuclear new build, the review has not so far considered whether nuclear should contribute to cutting emissions," it says.

Environment campaigners fear no solution has yet been found to the question of what to do with nuclear waste.

However critics claim "sustainable" solutions such as wind and sea power are unproven and expensive. They say nuclear power does have the potential to be green.

A decision on the future of Britain's power supplies needs to be taken early in Labour's third term as it could take at least 10 years for plans to be implemented.

The job has been given to new energy secretary Alan Johnson, but Cabinet rifts could make the task difficult.

Johnson's predecessor Patricia Hewitt was also thought to be sceptical of nuclear power, while Downing Street is said to be keen.

A DPEI spokesman said: "The government's energy policy is set out in the white paper. The new secretary of state, Alan Johnson, will need to look at the issue."