LONDON — The British government yesterday approved construction of the first new nuclear power plants in a generation, saying atomic energy could help fight climate change and secure the country’s energy supplies in an increasingly unstable world.

Britain joins a growing list of countries rethinking the long-unpopular nuclear option, driven by global warming, geopolitical uncertainty, and rising fuel prices. Environmentalists, however, condemned the move as an expensive and dangerous folly that would divert resources from the search for genuinely clean forms of energy. Energy Secretary John Hutton told the House of Commons that nuclear power “should have a role to play in this country’s future energy mix, alongside other low-carbon sources.” He also said nuclear energy was “tried and tested, safe and secure,” and that atomic energy was good for the environment and for national security.

Britain will move from producing most of its own energy to importing much of its oil and gas by 2020 as North Sea supplies run out, and the government has warned of the risk of becoming reliant on imports from unstable parts of the world. “Nuclear power will help us meet our twin energy challenges — ensuring secure supplies and tackling climate change,” Mr. Hutton said.

The government did not announce plans for specific new nuclear facilities but said it would consider proposals from international energy companies. Prime Minister Brown said the government was “inviting companies to express an interest in building a new generation of power stations to replace the existing ones.”

The announcement puts Mr. Brown’s government firmly on the pro-nuclear side of a debate that divides opinion across Europe. It’s a reversal for the governing Labour Party, which came to power in 1997 with a manifesto that said: “We see no economic case for the building of any new nuclear power stations.” Four years ago, the Labour government described nuclear power as an “unattractive” option.