The UK’s proposed investment in nuclear power means handing over control of energy policy to France at the same time as shouldering all of the risks associated with new reactors, four of the UK’s most eminent environmentalists have warned.

In an open letter to Prime Minister David Cameron, Jonathan Porritt, Tom Burke, Charles Secrett and Tony Juniper argue plans for eight new nuclear reactors, most of which are set to be built by French companies EDF and Areva, will prove “a massive rip-off for the British taxpayer”.

The government is keen to replace the UK’s aging nuclear power plants and last month signed a series of deals with France worth more than £500m to support plans for new reactors.

Cameron hailed the agreement as being “just the beginning” of co-operation between the two countries on nuclear energy.

But in today’s open letter the four former directors of Friends of the Earth argue that without a strong carbon floor price, which is effectively subsidised by UK taxpayers, the business case for new nuclear power does not stack up.

Without public funds, the companies – or the French government, which has large stake in both – could decide not to proceed, leaving the UK’s plans in ruins, they add.

They also warn that French operators could use the threat of such a scenario to secure further financial support, which may force up electricity prices for businesses and domestic customers.

“This is an invitation to EDF to bargain very aggressively for an agreement that transfers the lion’s share of the financial risk of new nuclear to British taxpayers and consumers,” the letter says. “EDF will have us over a barrel.”

Even if they do go ahead, “there is no reason to believe that Areva will be able to construct new reactors on time and to budget”, the letter adds.

The two next generation (EPR) generators being constructed at Flamanville in France and Olkiluoto in Finland are both severely over-budget and behind schedule.

The letter argues that instead of investing in nuclear power the government should focus on transforming the UK into an energy efficiency and renewable energy powerhouse.

“Ministers have been well and truly led up the garden path by the nuclear lobby,” said Tony Juniper.

“The Prime Minister needs to step in and make sure that energy policy is truly working in the public interest, rather than to the agenda of a massive vested interest.”

Supporters of nuclear power are likely to counter that the government has pledged to ensure that new nuclear reactors are built with no specific subsidy and that as such the carbon floor price mechanism supports all types of low carbon energy, including renewables and carbon capture and storage (CCS) plants.

A spokesman for Number 10 told BusinessGreen the Prime Minister would be responding to the letter privately and was unable to disclose details. However, he reiterated the government’s stance that nuclear power forms part of its vision of a balanced energy mix.