Almost three quarters of consumers (73%) said they were unable to work out if there had been a mistake on their energy bills, while 30% said the same for their water bills, the survey by price comparison website uSwitch.com found.
The figures follow a study in May by uSwitch that found consumers were overcharged by £6.7 billion on household bills in the last year, with 95% of cases spotted by consumers themselves.
The poll found 86% of consumers find energy bills too complicated, 73% believe they use too much jargon and 65% cannot find the information they need. More than eight in ten (82%) find energy bills harder to understand than any other bill, while 38% fear they have lost money because of a confusing energy bill. Despite this, 38% of consumers trust their gas or electricity supplier to get their bills right, while 21% trust their digital television provider and 33% trust their mobile phone company.
USwitch director of consumer policy Ann Robinson said: "In this day and age, clear and concise bills should be the very least that consumers should expect. The fact that some companies and industries are still unable to get this fundamental part of their service right is simply unacceptable.
"Supplying simple, straightforward and helpful bills is a vital part of building trust and consumer confidence. It helps to put customers in control and enables them to make informed decisions and choices about products and services. It also means that consumers stand a greater chance of spotting any inaccuracies or incorrect charges. This is also why, despite the difficulties, consumers must continue to check their bills carefully as failure to do so could leave them out of pocket."
Energy minister Greg Barker said: "The coalition is determined to do everything we can to help hard pressed families with the rising cost of living. That also means going further than any government before in simplifying energy tariffs. Baffling billing for gas and electricity is exactly why we're taking powers in the Energy Bill to help consumers."
An Ofgem spokesman said: "Ofgem has now confirmed its proposals for a simpler, clearer, fairer energy market for consumers. The first of our reforms - enforceable standards of conduct so suppliers treat customers fairly - will come into force at the end of next month. We are proposing that the main tariff reforms are all be in place by December 2013. Our reforms mean that for the first time suppliers will be limited to offering up to four core tariffs per fuel.
"They will have new rules to meet requiring all information they send to consumers to be simplified, more engaging and personalised to them. They must also be required to give all their customers personalised information on the cheapest tariff they offer for them."