Chancellor Gordon Brown has given a clear signal that he supports the building of new nuclear power stations.
Some MPs had hoped Mr Brown would take a different stance
In an article in the Times, he said the government was set to demonstrate its flexibility in key policy areas such as energy - "including new nuclear".
The government's energy review is due by the end of July but Tony Blair has already said he favours new plants.
The anti-nuclear lobby and some Labour MPs had hoped the expected next party leader would take a different view.
The UK generates about 20% of its electricity from nuclear power.
In recent weeks, Mr Blair has made it clear that he sees new nuclear power stations as part of a mix to fill the gap which will be left when the current sites come to the end of their lives.
In a speech at the CBI annual dinner in May, he said the issue was "back on the agenda with a vengeance".
And at a summit on Friday, French President Jacques Chirac announced the UK and France would be setting up a joint nuclear energy forum.
Mr Blair told a joint news conference in Paris he was not prejudging the outcome of the energy review, but said he believed it was a simple question of energy efficiency, self-sufficiency and climate change.
BBC political correspondent Gary O'Donoghue said anti-nuclear campaigners had hoped Mr Brown could be persuaded to modify such a policy. But that has all but vanished with the "unequivocal backing" for nuclear power in the Times article.
In the article, published to coincide with the G8 finance ministers meeting in St Petersburg, Mr Brown writes: "In Britain over the coming weeks and months we will demonstrate our enhanced flexibility with further reforms in planning, skills and labour markets, and in energy policy, including new nuclear..."
For the Tories, meanwhile, shadow trade and industry secretary Alan Duncan has said he opposes subsidies or price guarantees for nuclear firms.
The comments appear to make cross-party consensus on building a new generation of nuclear power plants unlikely.
The Liberal Democrats have already voiced their opposition to new stations.