Huge government subsidies to state-owned French and Chinese companies for a major new nuclear power station are "the worst deal of the century," protested Labour MP Paul Flynn yesterday.

Prime Minister David Cameron hailed the go-ahead for construction of two reactors at Hinckley Point C in Somerset as "a very big day for Britain."

But he came under fire for agreeing to pay the investing companies twice today's wholesale energy price for the entire first 35 years of operation.

French group EDF is expected to hold around 50 per cent of the equity, with a further 10 per cent held by reactor designer Areva, another French company with majority state ownership.

Chinese nuclear corporations CGN and CNNC will together hold a stake of between 30 and 40 per cent.

The British government will guarantee a price of £92.50 for each megawatt hour of power produced by Hinckley Point C, which is projected to begin operations in 2023 and provide 7 per cent of the nation's energy.

Unions welcomed the project, which will create up to 25,000 jobs during construction and around 900 permanent jobs when operational.

Five-hundred apprenticeship roles are also expected to be created.

Negotiations are also underway to build two further nuclear reactors at Sizewell C in Suffolk. If this project goes ahead, the guaranteed price at Hinckley will be slightly reduced to £89.50, based on "benefits" from shared design, supply and engineering.

Newport West MP Mr Flynn led a group of MPs expressing alarm at the costs to British taxpayers, warning of "massive future liabilities."

Mr Flynn told the Star: "This is the worst deal of the century."

He warned that nuclear energy technology was "fragile," had collapsed in Japan post-Fukushima and was being shunned by some other countries.

Miners' MP and coal campaigner Dennis Skinner was among MPs signing a critical early day motion tabled by Mr Flynn.

It also highlighted the £75 billion nuclear waste clean-up costs already being met by taxpayers.

General union GMB warmly welcomed the go-ahead for the new nuclear power station but urged "cast-iron guarantees" that the project would provide jobs in Britain.

"GMB has fears that Chinese manufacturers may gain from the nuclear renaissance in the UK while British companies miss out," said a spokesman.

Unite union national officer Kevin Coyne hailed the 500 new apprenticeships to be created.

"Nuclear power is a key part of a balanced, low-carbon energy policy," he said.

"At last the government has provided the stability and certainty the UK needs to begin to meet the huge energy challenges facing us," he said.

But CND general secretary Kate Hudson complained: "Instead of subsidising nuclear energy production, the government should be investing more in safe, clean and affordable renewable energy."