Britain's biggest 'green' power station is being investigated by the City watchdog – just months after being offered billions in new subsidies by Ed Miliband.

Energy company Drax yesterday revealed that the Financial Conduct Authority (FCA) had launched a probe into 'certain historical statements' regarding the sourcing of wood pellets used in its biomass plant in North Yorkshire.

The firm's shares plummeted by eight per cent following the disclosure.

It is embarrassing for Energy Secretary Mr Miliband as the probe comes just six months after he agreed to extend subsidies for the power station, which has long faced criticism from environmental campaigners.

Drax's most recent annual report suggested it received £869million in subsidies last year.