Government support for a new generation of nuclear power stations has been condemned, the day before it is formally announced in the Commons.
Business secretary John Hutton will make a statement on energy and nuclear power tomorrow, expected to signal government support for private companies to build and run up to ten nuclear power plants.
In its meeting yesterday the Cabinet reportedly agreed unanimously to support proposals which will include a streamlined planning process to encourage private investment.
The government argues nuclear power could provide up to 20 per cent of the UK's energy needs, reducing reliance on foreign supplies of gas and oil.
Addressing MPs in the Commons today, Gordon Brown said Britain is facing a "major decision" on the future of energy.
Mr Hutton's statement will outline the government's decision, he continued, with the alternative that Britain becomes more dependent on foreign supplies.
The prime minister said he was "shocked" that the leaders of the other two main political parties were not backing the government on nuclear power.
Criticising Mr Cameron's measured support, Mr Brown said: "Nuclear as a last resort; that is not the proper way to plan the energy needs of this country."
The Liberal Democrats are among those criticising the likely proposals, which will place the onus on private energy companies to finance nuclear power.
Lib Dem leader Nick Clegg said the government must be honest about the cost of building and running new nuclear power stations.
Mr Clegg said: "Nowhere in the world has a nuclear power station been constructed in recent years without significant state help.
"Even if energy companies could run them without taxpayers' money, consumers would just end up paying for them through higher fuel bills."
The Liberal Democrats are urging the government to abandon its "expensive white elephants" ahead of tomorrow's announcement and focus on energy efficiency and genuinely renewable technologies.
This argument was reiterated by Friends of the Earth (FoE), which raised concerns the government's "focus" on nuclear power will distract it from renewable energy and energy efficiency.
FoE director Tony Juniper said: "The decision to encourage the construction of new nuclear stations in the UK is both irrational and unfortunate.
"It is irrational because the economics do not stack up and because renewables and energy efficiency could meet our needs more quickly and sustainably.
"It is unfortunate because the nuclear option will limit our ability to lead in the exciting and fast growing new markets for modern energy sources. And that is bad news for the UK economy and jobs."
The Green party has also pre-emptively condemned the government's approval.
Green MEP and principal speaker Caroline Lucas said the prime minister was "guilty of the most staggering failure of political vision".
Ms Lucas argued: "It simply isn't true that nuclear power is the answer to the so-called energy gap we face over the next ten years, since the earliest that a new nuclear power station could come on stream is around 2017."