The Cabinet has agreed in principle to approve a new generation of nuclear power stations, it has emerged.
Ministers backed the principle of the plans without a vote.
Business Secretary John Hutton will formally announce the decision in a statement to MPs on Thursday.
Environmental campaigners say such a move will be expensive and dangerous. Greenpeace says atomic power will not meet the projected energy shortfall.
But Gordon Brown has said the decision is "a fundamental precondition of preparing Britain for the new world".
He refused to be drawn on the detail when the matter was raised at his monthly Downing Street news conference.
However, his Cabinet unanimously backed the principle of the plans without a vote.
In Sunday's Observer, the prime minister said: "When North Sea oil runs down, both oil and gas, people will want to know whether we have made sure that we've got the balance right between external dependence on energy and our ability to generate our own energy within our own country, and that's about renewables as well as about other things.
"And so the willingness to take tough long-term decisions, whether it's wind power or wave power, whether it's renewables generally or nuclear, is I think a fundamental precondition of preparing Britain for the new world."
The prime minister's spokesman said firms which build any new nuclear stations - if they are given the go-ahead - would have to fund any future decommissioning costs.
He added: "We have always been clear that the full share of the costs of the long-term management and disposal of waste should fall on the operators."
The then prime minister Tony Blair said in 2006 that the government believed new nuclear stations should be built.
But that decision was put on hold after the consultation element of the initial energy review was ruled "seriously flawed" and "misleading" by a High Court judge, following a challenge by Greenpeace.