Gas bills could rocket by 15 per cent

The price rises, which could come as early as February, would add £85 to a typical family's gas bill, pushing it up to £653 a year.

Consumer groups accused suppliers of "tacitly colluding" to talk up the price of wholesale gas to justify the "unnecessary" increases.

Total energy bills for millions of consumers have already risen by 50 per cent since 2004, with many paying more than £1,000 last year.

It meant around one in three local authority households - some 650,000 - struggled to meet fuel bills last year, paying an average of £814 a year compared with £590 in 2004.

Yet just six months ago many big energy firms reported bumper earnings, including record half-year profits for British Gas of £533million.

Last month, it emerged that food prices are also rising at their fastest rate for 14 years, after the price of basic ingredients such as wheat increased by 6 per cent. This could add up to £1,000 to a family's annual grocery bill.

The average price of petrol also surged past £1 a litre last month - meaning the typical driver is £15.33 a month worse off than in 2006.

In March, British Gas slashed its prices after the price of wholesale gas fell by 50 per cent. The reduction saw the average gas bill fall 17 per cent to £568, while electricity bills also fell by 11

per cent to £381. Since September, however, wholesale gas prices have risen by 38 per cent.

This led Catalyst, a leading energy broker, to warn prices could go up by 10 per cent in the new year. The Russian gas giant Gazprom, which supplies a quarter of Europe's gas, went even further, warning of a 20 per cent rise.

But Allan Asher, chief executive of the consumer group Energywatch, claimed gas firms were exaggerating the possibility of supply problems over the winter to prepare the market for the price rises.

He added: "Just because there is now an increase in the price of wholesale gas, it does not mean there is a need to increase prices."

Joe Malinowski, founder of the price comparison website theenergyshop.com, said: "The question is whether companies should absorb the costs because of the extraordinary profits they made in 2006. It would be extremely harsh on the consumer if the price was off-loaded onto them."

A spokesman for British Gas's parent company, Centrica, said: "British Gas intends to remain competitive as we have been all this year after leading the industry down in March and April."