Labour backbench MPs are to mount a campaign urging the prime minister not to build more nuclear power stations.
Mr Blair has faced protests from anti-nuclear campaigners
The group is launching a manifesto to promote investment in renewable energy, saying the government would be taking a "dangerous leap with nuclear".
Tony Blair has launched an energy review, amid reports he sees building more nuclear power stations as the only way to meet future needs.
Ministers say they have so far made no decisions on building new plants.
'Change in attitude'
The anti-nuclear campaigners - led by former minister Alan Whitehead - say the government will have to subsidise the nuclear industry massively to make new stations viable.
The move to produce an alternative manifesto mirrors the tactics taken against the government's education reforms, in which those MPs opposed to the idea set out their own proposals.
Mr Whitehead told the Guardian newspaper: "We have been promised by government that there is a debate to be had and that no decisions have been made.
"But there is a change in attitude in government. Only three years ago, a White Paper pretty well ruled out nuclear. But it is now at centre stage."
He claimed nuclear power stations could not be built if there were "no assistance for new nuclear build, no long-term promise of a guaranteed market and no minimum price for nuclear".
The Guardian reports that two members of the environmental audit select committee, David Chaytor and Colin Challen, are involved.
Speaking at the launch of his energy review in November, the prime minister said renewable sources could fill some but not all energy gaps.
But many Labour MPs fear Mr Blair privately favours renewing investment in nuclear energy, to keep targets on climate change.