The announcement, made at a summit on Friday between the French president, Jacques Chirac, and the British prime minister, Tony Blair, increased speculation that London was planning to build a new generation of nuclear plants to replace Britain's ageing reactors.

Blair said: "One thing is for sure, this policy, for reasons of energy security, is right at the top of the agenda.

"But there is of course another reason why energy policy is dominating thinking around the world and that is the challenge of climate change."

The agreement bound the two sides to no more than exchanging ideas on issues such as decommissioning and waste management.

Energy needs

But the pact adds to growing signs that nuclear power, the image of which has suffered hugely in Europe in the wake of the Chernobyl disaster two decades ago, is making a comeback.

Blair's government is due to publish a review of Britain's energy needs this month which is expected to back the construction of new nuclear power plants, although he said he did not want to prejudge the outcome of the review.

Britain's nuclear power stations supply 20% of the nation's electricity, while in France nearly 80% of electricity comes from its extensive network of nuclear plants.

"Nuclear energy is one of the ways of responding to the energy problems of tomorrow," Chirac said. "It is legitimate that two countries like France and Britain are keen to work together, think together and come to the same conclusions."