"The issue back on the agenda with a vengeance is energy policy," Blair said on Tuesday in a speech at a hastily erected podium after a protest by anti-nuclear campaigners forced officials to change the venue at the last minute.
"Energy prices have risen. Energy supply is under threat. Climate change is producing a sense of urgency."
Nuclear power provides a fifth of Britain's electricity, but the nation's 12 nuclear power plants are ageing and unless replaced will provide 4% by 2010.
A government policy paper on energy resources that will be issued by the middle of 2006 will address the possibility of a new generation of nuclear power stations that could provide enough energy for the country, Blair said.
"In Britain, on any basis, we also have the issue of our transition from being self-sufficient in gas supply to being an importer," he said.
Activists worry that more nuclear power plants would hurt the environment.
Earlier on Tuesday, two activists from the environmental pressure group Greenpeace clambered high into the rafters of the hall in Islington, in north London, where Blair was to speak.
Activists worry more nuclear
plants will hurt the environment
Dressed in suits and ties, the pair wore high visibility vests and appeared to have security passes. They used safety harnesses to attach themselves to the frame of the roof and sprinkled hundreds of yellow stickers bearing an anti-nuclear slogan onto the delegates below.
Conference organisers said Greenpeace offered to end the protest in exchange for 10 minutes to speak before Blair - a request rejected by Digby Jones, director general of the Confederation of British Industry.
Security staff cleared the hall of delegates and Blair instead spoke in a cramped room where participants were forced to stand.