Soaring energy bills have left an estimated 5.5 million UK households in debt to their gas and electricity suppliers.

Research revealed that a massive £728 million is owed to energy suppliers and is part of a backlog that saw gas and electricity prices rise by 42% in 2008.

The effects of the prices hikes are still being felt two years later with the average customer owing £132 in debt, according to research from price comparison site uSwitch.com. Bill prices did drop in 2009 but only by 4% on average.

Four of the big energy suppliers have announced price cuts for 2010 of around 7% but this will do little to return the prices to their pre-2008 rates.

The director of consumer policy at uSwitch, Ann Robinson, said: “The fact remains that consumers have been left facing bills that are almost £300 higher than at the beginning of 2008.

“This has clearly taken its toll, yet again raising serious concerns about the affordability of energy in this country.”

Last month uSwitch carried out another survey which showed that one in eight people in the UK owe less than £100, while around 2% owe between £200 and £300, in a survey of 2146 people.