Britain's largest energy provider used a trading update to warn that the price for gas in the wholesale market had risen so significantly and that "if sustained, (will) create a more difficult environment for retail energy suppliers in the U.K. going into 2008".

The announcement comes less than two weeks after the company announced increases to its gas and electricity tracker tariffs that could affect the majority of the company's 16 million customers, The Independent reported Saturday.

Analysts are predicting increases next year of about 15 per cent for gas and electricity bills, due to the rising prices of natural gas and coal, which are used to generate electricity.

Centrica, as one of Europe's leading energy suppliers, is typically the first to increase its rates, with its rivals usually following suit, the newspaper reported.

"Historically, when one of the big suppliers increases prices, the others are quick to follow," said Karen Darby, of the price comparison service SimplySwitch.