Scottish & Southern Energy (SSE) will raise its prices from September.
The company says that household gas bills will rise by an average of 18 per cent and electricity costs will increase by 11 per cent.

SSE says the price rise is due to an increase in wholesale energy prices. British Gas has already announced that it will be raising the cost of electricity and gas from the 18 August, and Scottish Power has also said prices will rise in June, with the cost of its gas going up by 19 per cent from the start of next month, and its electricity rising by 10 per cent.

Mike O'Connor, chief executive of Consumer Focus, the statutory consumer organisation, said: 'Knowing another price rise was round the corner will not soften its impact for customers. This increase heaps more pressure onto already cash-strapped consumers and will tip many thousands more people into fuel poverty. Currently, consumers cannot tell whether these increases are justified and that stokes the lack of trust in energy firms. Suppliers point to rising wholesale costs. Yet although wholesale prices have risen recently, they remain around a third lower than their 2008 peak.

'Ofgem must get to the heart of whether prices are fair. If the regulator can't do that it must refer the market to the Competition Commission. The Commission is not there to punish companies, but to use its forensic skills and experience to find remedies for complex markets which are not serving consumers well. We are pleased that Ofgem has said it is prepared to refer the energy market if necessary, but it must be prepared to act.'

Consumer Focus has suggested a number of measures to reform the energy market so that the Big Six energy companies will treat their customers more fairly. The organisation also wants a competition review of the structure of the energy market and moves to improve transparency so Ofgem can judge whether consumer bills are fair. Additional measures include a boost to the number of new entrants to the market, a clear strategy to help cut consumers' bills and reduce fuel poverty and an end to complex tariffs and cold-call doorstep sales.

Mr O'Connor continued: 'It is clear that this is a critical moment for the energy market. As well as volatile gas prices, huge investment in cleaner power plants and other low carbon programmes will push bills up considerably. So consumers need to be confident that prices are fair. Government must make sure measures to cut carbon emissions and break away from imported fossil fuels are cost effective and run alongside radical programmes to cut energy use.'