4 million consumers complain about energy bills, says Which? The complaints covered a wide range of issue, with the vast majority relating to billing. Last year the average household bill rose by around a fifth to £1,300. But Which? also found that nine out of 10 unsolved complaints were not taken to the energy ombudsman for resolution. More than a fifth of those surveyed who had suffered problems with their energy supplier in the past year admitted they did not make a complaint at all. Customers can take their complaints to the energy ombudsman for free, but only if it remains unsolved after eight weeks or the supplier sends a deadlock letter saying it can do no more. The results, compiled over the 12 months to September last year, suggest that tens of thousands of households are being overcharged for their monthly direct debits. It means that an estimated £4 million in compensation may be going unclaimed every year. Richard Lloyd, executive director at Which?, said that the Government "must do more to answer the fundamental questions about why the energy market is allowed to work against the public interest." "Energy suppliers should be held publicly accountable, on a regular basis, for putting right the problems their customers are reporting," he said. It is a sign of the level of frustration with this industry that so many people have a problem but don't complain, even when they could be missing out on compensation. On Tuesday, Keith Anderson, the Scottish Power chief executive, admitted that his firm failed to "listen properly to what our customers were saying" over energy bills. He said that for every £1000 fuel bill, Scottish Power made £10 profit. "I really, really do understand how difficult it is for people," he told ITV News. We are working in an industry where over the last three or four years, for an average customer who is paying £1000 for a dual fuel bill, we are actually only making ten pounds of profit in that part of the business. What we try to do with all of our customers is look at what are their personal circumstances. What's the most appropriate product for them. He added: ..."What we're trying to do is better communicate and better explain to people how it is we make money and where it is we make money. Because we're not making a lot of money from physically selling the product. Pressure is mounting on energy companies to cut household bills after separate research showed the price of gas and electricity on world markets has tumbled in recent months. Earlier this week Energyhelpline.com said that household bills should fall by as much as £135 a year as a result of falling prices on the so-called wholesale market. On Tuesday night, Ofgem, the energy regulator, said that it is seeking greater powers from the Government to allow it to publish complaints data. A spokeswoman said: "Ofgem is seeking greater powers from government to grant us responsibility to publish complaints data after the closure of Consumer Focus. We have already taken strong action against energy companies on this issue and fined npower £2 million and British Gas £2.5 million for poor complaint handling.