Nuclear energy is not the "sole answer" to meeting UK energy needs but failing to consider it would be a "dereliction of duty", Tony Blair has said.
Mr Blair has raised the prospect of new nuclear power stations
At prime minister's questions, Scottish National Party MP Mike Weir accused Mr Blair of threatening to leave a legacy of nuclear "dumps" in Scotland.
Mr Blair sparked anger on Tuesday when he said new nuclear plants were back on the agenda "with a vengeance".
But he told MPs the UK risked being left reliant on foreign energy imports.
He told Mr Weir waste from existing nuclear plants had to be disposed of in any case.
"We have to address the energy needs of this country in the future," he added.
Critics accused the prime minister of pre-empting the government's energy review, which is due to report in July.
Earlier, ex-Labour environment minister Elliot Morley rejected the case for a new generation of nuclear plants.
He told The Guardian newspaper the energy review, which is headed by Department of Trade and Industry Minister Malcolm Wicks, might well point to renewable sources of energy if it was "open, transparent and fair".
Elliot Morley says environment ministers were not involved enough in the energy review
He complained that the Department for Environment, Food and Rural Affairs had not had the involvement it should in the technical aspects of the review.
He had seen no official government figures on the real cost of nuclear power.
Mr Morley said: "To have new nuclear power is going to involve very large sums of money.
"If nuclear power was so great then you would have the private sector willing to invest in it.
"The reality is that economically the risks are great and the returns are low.
"No private sector company is going to take on the long-term risks, the cost of decommissioning, the storage, reprocessing and the responsibility for the waste."
The recent reshuffle saw David Miliband become environment secretary, replacing Margaret Beckett, who was seen as a nuclear sceptic.
Friends of the Earth's Tony Juniper said: "It's probably no coincidence that a number of nuclear sceptics were removed from key Cabinet posts earlier this month."
Mr Blair told the CBI on Tuesday he had seen the "first cut" of the energy review.
He said if current policy remained unchanged there would be a "dramatic gap" on targets to reduce CO2 emissions by 2025 forcing Britain to become heavily dependent on gas.
"We will move from 80 or 90% self-reliance on gas to 80 or 90% dependency on foreign imports, mostly from the Middle East, Africa and Russia," he told business leaders at the CBI.
These "stark" facts "put the replacement of nuclear power stations, a big push on renewables and a step change on energy efficiency, engaging both business and consumers, back on the agenda with a vengeance," Mr Blair added.
The Conservatives accused Mr Blair of trying to reassert his authority in government by "trampling" over his energy review.
The Liberal Democrats described the move as another "desperate attempt" to establish his legacy.
The remarks were seized upon by environmental campaign groups.
Stephen Tindale, spokesman for environmental group Greenpeace, said: "The prime minister obviously made up his mind about nuclear power some time ago, and certainly well before the government launched its energy review.
"The review is a smokescreen for a decision that has already been taken."
And Sir Jonathon Porritt, chairman of the Sustainable Development Commission, said: "It would be damaging to this government's credibility if it were to pre-empt the conclusions of its own energy review, by making premature and insufficiently considered announcements on nuclear power."
The commission, which is an independent government watchdog, recently produced a report that said nuclear power was not the answer to tackling climate change or security of supply.