Jean Bernard Levy, the EDF group chief executive, and the French and British governments, have in recent days insisted they are as committed as ever to a positive final investment decision being taken as soon as possible.

But well-placed sources in Paris have told the Guardian that the already divided EDF board, which must make that decision, is in danger of fracturing further as former supporters of the project worry about Brexit.

“The situation for Levy was already very delicate,” said one source. “But it has become a lot more difficult because there is so little certainty around the British government,” they added. “No one could know today which way a vote [of the board on Hinkley] would go.”

Those arguing against the project say it is impossible to make any decisions when it is unclear who will be the future prime minister, chancellor of the exchequer and energy and climate change secretary.

Highly critical EDF unions in France, which have six representatives on the main board, are pressing waiverers among the five independent board members who have previously supported Levy to change their minds.

Growing concern has led to four British trade unions urging EDF to press ahead with Hinkley.

It was a first “litmus test” that major infrastructure projects will proceed as normal following the Brexit vote, they argued. …”