British Gas - the UK's biggest supplier of domestic energy - is putting up gas prices by 35% and electricity by nine percent.
Customers on dual tariffs will see their bills rise by 25%.
The firm blames soaring wholesale energy prices for the increases, which come after a similar move by rival EDF Energy last week.
They will come into effect immediately and will add an extra £262.80 a year to the average dual fuel customer's bill, or 72p a day.
The company, which owned by Centrica, blamed increasing global demand, diminishing UK gas reserves and record oil prices for the decision.
But it said standard rate customers will not be hit with any further prices rises this year.
British Gas said it is currently running at a loss as it struggles to cope with an extra £2 billion in costs.
Wholesale gas prices for the coming winter were 89% ahead of last year.
These have wiped more than two-thirds off its profits for the first half of the year, which fell by 69% to £166 million.
This compares with the bonanza £533 million when the firm waited before passing on previous falls in wholesale energy costs.
It says it has also been hit by higher transport and distribution costs.
Source: http://uk.biz.yahoo.com/30072008/140/massive-rise-energy
-prices.html
