ASN, the French nuclear watchdog, said that state-owned EDF would have to repair eight faulty weldings in the reactor's containment building, adding that it had rejected a request to delay repairs until 2024.

The decision could mean the Flamanville startup would again be delayed by two or three years from the most recent startup target of loading fuel in the reactor by the end of this year.

France's Economy minister Bruno Le Maire told BFM television on Friday that "incidents" at Flamanville, northern France, were "unacceptable", adding that he had asked a former executive with car maker PSA, Jean-Martin Folz, to conduct an independent inquiry.

Le Maire did not elaborate on a timeframe.

EDF wants to build new reactors as its current fleet is ageing.

Flamanville's problems have weighed heavily on the future of the nuclear industry in France as well as EDF's export prospects.

(Reporting by Matthias Blamont; Editing by Louise Heavens)