George Osborne says he is "concerned" by a rise in energy prices announced by two major suppliers.

The announcement came after British Gas announced an extra £80 on to its typical annual dual fuel bill with an average increase of 6 per cent affecting 8.5 million customers from November 16.

Rival Npower followed with an average rise of 8.8 per cent for gas and 9.1 per cent for electricity. Both companies blamed rising costs largely outside their control.

The announcements have raised demands from unions and consumer groups for Government action to tackle rising fuel prices.

Chancellor George Osborne urged the firms to reconsider the price rises, which have sparked warnings of households being plunged into a "long, cold winter".

Mr Osborne told ITV News the Government had programmes to try to help people reduce their household energy costs.

"Of course I'm concerned when I see electricity bills going up and partly that is because of things beyond our control - what's happening in the world with oil prices and gas prices," he said.

"We've also got to do everything we can in Britain to try and keep those bills down.

"I would urge those energy companies to look again at any increases to see if they are absolutely necessary at a time like this."

The pre-winter move from British Gas comes months after parent Centrica posted a 23 per cent rise in half-year profits at its residential arm to £345 million.