Price hikes by energy companies have left nearly four million customers in debt to their suppliers with an average bill of £131 per household, new research reveals.
Across the UK this works out at a debt of £478 million owed to the suppliers, according to uSwitch.com.
This figure is 4% higher than a year ago, and 15% higher than in 2008.
"With households still struggling to absorb last year's price hikes, energy debt is on the rise again," says Ann Robinson, director of consumer policy for uSwitch.
Although energy companies have recently cut their prices, the average household energy bill is now £1,252 year - a massive £183 higher than a year ago.
Of those in debt, one in five families plan to pay this off through a lump sum while 42% will meet the payments by increasing their direct debits. But research from uSwitch shows the average household could save £420 by switching energy providers.
Robinson adds: "Those in energy debt can face a catch-22. Despite knowing they could reduce their bills by moving to a cheaper energy plan, consumers can see debt as a barrier to switching."