ScottishPower has become the latest British power supplier to announce a double-digit price increase, compounding winter misery for millions of British consumers struggling to deal with rising prices for fuel, food and a range of other household bills.

The company, which has 5.2 million customers and is owned by Iberdrola, the Spanish utility, said that, with immediate effect, electricity prices would rise by an average of 14percent and gas prices by 15 per cent.

The announcement came as heavy snow blanketed much of Scotland and northern England and follows double-digit price rises implemented last month by British Gas, npower and EDF. Powergen, which is owned by E.ON, of Germany, is also believed to be on the brink of raising prices for its customers, Scottish and Southern Energy, another supplier, has pledged to freeze prices until at least the end of next month.

ScottishPower pinned the blame on the rising wholesale prices of coal and gas. Willie MacDiarmid, the director of energy retail for the company, said: “Our input costs are now at record levels, having increased by up to 97 per cent since February 2007. Like other energy providers, we are now forced to pass on some of these higher costs.”

Tim Wolfenden, the head of home services at uSwitch.com, said that the price increase meant that average bills for dual-fuel customers of ScottishPower had reached £1,100.

The announcement came days after Ofgem, the industry regulator, revealed that it had examined claims of cartel-like activity in the British retail energy market.

Last month Ofgem sought reassurances from the Energy Retail Association that regular meetings of the group, whose members include the six leading British suppliers, were not being used to discuss pricing. The regulator said yesterday that it had found no evidence of anticompetitive behaviour.

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