Consumers are facing another round of energy price rises after the UK's biggest supplier revealed a further squeeze on its margins.
British Gas owner Centrica said the wholesale price of gas and power for delivery next winter is around 25% higher than last year, but the price paid by households has yet to reflect this higher price.
The company, which has around 16 million energy accounts, said its results for 2011 were likely to be "materially influenced" by the recovery of higher wholesale prices and other costs.
It said: "Market conditions for our residential energy supply business are significantly more challenging than in 2010."
A Centrica spokesman said the company had yet to take a decision about whether to increase tariffs.