Almost four million households are in debt to their energy supplier, owing an average of £128, according to a survey.
Debt among the 14% of households that owe money has increased by £5 on last year, despite the mild winter, following a series of price hikes, the poll by uSwitch found.
The average household energy bill is now £1,265 a year, £53 more than a year ago and £793 or 168% higher than in 2004.
A third of those in debt owe more than they did a year ago while 9% owe less, the survey found.
A quarter of households are choosing to “turn a blind eye” to their debt in the hope that the amount will decrease over time, 21% intend to pay it off with a lump sum, and 43% plan to increase their direct debit.
However, worry over mounting debt is leading almost one in 10 (9%) to seek a repayment plan with their energy supplier.
Ann Robinson, uSwitch director of consumer policy, said: “Millions of households are in debt to energy suppliers and the amount they each owe has risen.
“This is a clear indication of the extreme pressure families are under to meet the rising cost of energy. The average household energy bill is £53 a year dearer than a year ago. For many consumers, the only thing that has kept this particular wolf from the door is the fact that this winter has been exceptionally mild.
“Those in energy debt can face a catch-22. Despite knowing they could reduce their bills by moving to a cheaper energy plan, many see debt as a barrier to switching.
“With a difference of over £300 between the cheapest and most expensive tariff on the market, consumers cannot afford to have this avenue closed to them.”
A spokeswoman for the Department of Energy and Climate Change said: “The government is doing everything within its power to help hard-pressed families keep their energy bills down.
“In December we announced plans that will save customers around £50 on their energy bills, protecting support through the ECO scheme for vulnerable households, extending the scheme for an extra two years, and making an additional £450million to make Britain’s homes more energy-efficient.
“This is on top of the support already available to vulnerable households through schemes like the Warm Home Discount, whereby well over one million low-income pensioners who will receive £135 off their bill, and Winter Fuel Payments.”