Le Monde said that the first conclusions of an internal review of the project showed that construction initially slated for end-2025 was not likely to start before 2027.

"The first conclusions...show there will be a financial overrun tied to calendar delays," several sources close to the matter said.

EDF declined to comment.

Hinkley Point C is Britain's first new nuclear plant to be built in decades. It has been plagued by delays and criticised for its guaranteed price for electricity, which is higher than current market prices.

EDF's UK arm EDF Energy is building the 18 billion pound plant in southwest England with China General Nuclear Power Corporation (CGN), which has a 33.5 percent stake.

(Reporting by Dominique Vidalon, Geert de Clercq; Editing by Toby Chopra)