The contract for a French-Chinese consortium to build Britain's first nuclear plant in a generation was signed on Thursday at a low-key ceremony, after a string of controversies threatened to scupper the huge deal.

The British government had delayed agreement over concerns about China's involvement, while there were also questions about how the French state-owned power giant EDF would fund the construction of Hinkley Point.

The contracts marked "a significant step forward for a new era of nuclear power in the UK", Britain's business minister Greg Clark said in a statement after the signing, which was also attended by French and Chinese officials.

Britain finally gave the go-ahead earlier this month for the 18 billion pound (21 billion euros, $23 billion) complex, which is expected to provide seven percent of the country's power needs, but it set conditions for the deal.

The government has said EDF cannot cede majority control of the project and wants more scrutiny over national security concerns for future projects.

EDF's board gave its go-ahead on Tuesday for the project in Somerset, southwest England, which will not be operational until 2025.

China has a one-third stake in the project and analysts had warned that Britain could have jeopardised relations with the world's second-largest economy if it scrapped the deal.

Critics said it could give China the power to turn off the lights.

Jean-Bernard Levy, chief executive of the French state-owned power company EDF, said this month that the move "relaunches nuclear power in Europe".

He said Thursday's ceremony marked a "milestone for those who have worked for so long" on the project.

The British government has said the plant's construction will create 26,000 jobs and "a huge boost to the economy".

Following the signing ceremony French energy company Areva announced it had won subcontracts related to Hinkley Point worth more than five billion euros ($5.6 billion, 4.3 billion pounds).

Areva said the contracts included the delivery of the two nuclear steam supply systems, fuel supply, and safety at the plant, with work due to start in the early 2020s.

- 'National security' test -

One of Downing Street's prime concerns was over the security implications of allowing China to take such a large stake in a critical infrastructure project.

Beijing's state-run China General Nuclear Corporation (CGN), the Chinese investor in Hinkley Point, was also set to take the lead in the Bradwell power station project in Essex in southeast England.

Olivia Gippner, a fellow in EU-China relations at the London School of Economics, said the framework was aimed at China but "by introducing a general national security test rather than focusing only on Chinese investment, this is a very diplomatic solution."

Chinese state media earlier this month had also welcomed the approval, but accused Britain of suffering from "China-phobia".

"Let us hope that London quits its China-phobia and works with Beijing to ensure the project's smooth development," the Xinhua news agency said in a signed commentary.

CGN is set to finance 6.0 billion pound of the cost of the Hinkley Point plant, with EDF providing the remaining 12 billion pounds.

Critics have focused on an electricity price guarantee to be paid to EDF of 92.5 pound for every megawatt hour of power produced by Hinkley for the next 35 years, rising with inflation, despite falling energy prices.

The project is strongly opposed by environmentalists.

"The UK government is about to sign away billions of pounds of billpayers' money to a project bedevilled by legal, financial and technical hurdles," said John Sauven, executive director of Greenpeace UK.

"Theresa May cannot build a 21st-century industrial strategy around an outdated, dodgy, and ludicrously expensive technology," he said.