See British Energy's shares

The delays affect its Hinkley Point nuclear power station in Somerset and Hunterston plant in Scotland.

British Energy said that following repair work on boiler pipes at the two sites it had found evidence of defects in another part of the boilers.

Last month, the firm warned repairs at the sites could be completed as early as January or as late as March.

British Energy is one of the UK's biggest energy suppliers, capable of providing one-fifth of the UK's electricity needs.

At close of trade its shares were down 35.5 pence at 538.25p.