In a "re-evaluation of the schedule and costs", EDF judged that the Unit 1 reactor at Hinkley Point C would become operational between 2029 and 2031, rather than the previous target of June 2027.

The total cost of the project would come in at up to "pound34 billion in 2015 values".

EDF cited "risks inherent in the ramp-up of the electromechnical work and the testing schedule" as reasons for the possible delay beyond 2029.

Hinkley Point C is one of a small number of European Pressurised Reactors (EPRs) worldwide, a next-generation design from EDF that has been plagued by massive cost overruns and construction delays.

Once operational, the plant would generate "around seven percent of national consumption" of electricity in the UK, EDF said.

The announcement of the new delay follows Prime Minister Rishi Sunak's announcement this month of Britain's "biggest expansion of nuclear power for 70 years".

"Nuclear is the perfect antidote to the energy challenges facing Britain -- it's green, cheaper in the long-term and will ensure the UK's energy security," Sunak said on January 11.

EDF's statement also comes as France is expected to announce a swathe of new reactor construction in an upcoming energy planning law.

France's only EPR project to date, at Flamanville in Normandy, has also suffered delays and budget overruns.

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AREVA