Labour conference: Business backlash over energy bills pledge 25 September 2013 Last updated at 00:56 Ed Miliband says energy firms will "not like" the move but it is necessary Ed Miliband is facing a backlash from energy firms after saying they would not be able to raise prices for the first 20 months of a Labour government. His pledge to freeze UK bills if Labour wins the 2015 general election has been welcomed by consumer groups angry at price rises over the past five years. The "big six" suppliers have warned a freeze could have serious consequences. But Labour dismissed as "absurd" their suggestions that the policy could lead to energy blackouts. The plan for a freeze on household and business energy bills between June 2015 and the start of 2017 was the stand-out announcement of Mr Miliband's party conference speech on Tuesday. Overcharging The Labour leader argued firms had been "overcharging" customers for many years and millions of households would benefit from the temporary cap on prices at a time when finances were under acute pressure and many were struggling to heat their homes. Labour says the move will save average households £120 a year and businesses £1,800. Mr Miliband insisted he wanted energy suppliers to be successful and to continue to invest in new capacity to supply the UK's long-term energy needs. Centrica's boss warns that the plan could lead to firms' "economic ruin" But he said "public consent" for these arrangements depended on consumers getting a fair deal and that could happen only if the energy market was totally restructured to separate firms' generating and retail operations. Labour has rejected suggestions the cap, which could cost energy firms £4.5bn, will endanger much-needed investment in new plants, saying suppliers should be able to absorb the cost of the freeze out of recent profits. Since 2007, gas bills have risen by an average of 41% in real terms, while electricity has gone up by 20%, according to the Office for National Statistics. This has contributed to overall industry profits of £2.15bn in 2009, £2.22bn in 2010, £3.87bn in 2011 and £3.74bn in 2012. Energy security risk But suppliers say prices have gone up to cover their rising environmental and social obligations and in response to commodity price rises - sums paid on wholesale markets. Speaking at a fringe meeting on Tuesday evening, a senior British Gas executive suggested such a direct price intervention could "threaten energy security in the UK." "If we have no ability to control what we did with the retail prices, and that (wholesale price volatility) was to happen again, it would mean we are selling products at significant amounts of a loss and that would threaten energy security in the UK," said Ian Peters. Asked whether it could mean "the lights could go off" he replied: "I think that is a risk." Energy Watch, the trade body representing the six largest energy firms, has described the price freeze as "superficially attractive" but suggested it could bring a halt to future infrastructure projects. Chief executive Angela Knight said: "It will also freeze the money to build and renew power stations, freeze the jobs and livelihoods of the 600,000-plus people dependent on the energy industry and make the prospect of energy shortages a reality, pushing up the prices for everyone." And the chairman of Centrica - British Gas's holding company - said a firm unable to control either its costs or its prices was potentially in danger of "economic ruin." "We are all concerned about rising prices and the impact on consumers, but we also have a very real responsibility that we find supplies to make sure the lights stay on," Sir Roger said. Labour's business spokesman Chuka Umunna told the BBC's Newsnight claims that the policy could see the lights go out was "patently absurd" and "nonsense" put about by the large energy companies. He suggested they had under-invested in the past. Energy regulator Ofgem, which Labour plans to replace after 2015, has suggested legislation would need to be passed to change pricing arrangements. In his speech, Mr Miliband also promised Labour would build 200,000 new homes a year by 2020 and enfranchise 16 and 17 year olds.