Scottish Power, E.ON, Npower and Scottish & Southern Energy (SSE) are all thought to be preparing further price increases in the coming days.

The rises come despite apparent cost deductions. The price of next-day gas delivery has dropped 32% over the past month, from 69p per therm in early July to 47p last night.

Forward gas prices have also fallen. The price of delivering gas this winter has declined from 104p per therm last month to around 88p per therm.

Crude oil prices, to which most commercial gas contracts are linked, have also dropped by nearly 20%. Barrels reached a high of $147 per barrel on July 11 but are now at around $118.

Mark Snee, managing director of Technoprint, said: “Our costs have nearly doubled since June. We have a contract with N Power and it’s costing us an extra £2,000 per year. Printers are really struggling with this and our margins are tight enough already.

“The government talks about tax breaks for pensioners, but there can be also be serious effects if rising costs force a business to go bust.”

Energy companies buy their gas using a variety of short- and long-term contracts, so some are more exposed than others to fluctuations in wholesale markets.

EDF was the first major energy company to announce price rises for its five million UK customers two weeks ago. It was followed last week by British Gas, which increased prices in some regions by as much as 44%.

It blamed soaring wholesale energy costs and the need to import more supplies because of the depletion of stores in the North Sea. British Gas also said that it needed to raise prices to ensure it could invest in new sources of low-carbon energy.