It follows checks on reactors at Scotland's Hunterston plant, which showed problems with cracked pipes.

British Energy said it did not believe the position at Hinkley B - which has identical reactors - was as serious.

But as a prudent measure, the date of the station's three-yearly statutory inspection has been brought forward.

The advanced gas-cooled reactors (AGRs) at both Hunterston and Hinkley B are 30 years old.

The company said the level of cracking in boiler tubes at the Scottish plant was "above that expected." Repairs are currently being made to the defective pipes.

Hinkley B's two reactors provide 3% of the UK's electricity, but output has been cut by half, with the closure of one of them for early inspection.