Household are already lumbered with a record £1.3billion of energy debt - as experts predicted average bills will surge to more than £4,400 next year.
Research published today by the price comparison website Uswitch reveals the amount customers owe to energy suppliers is nearly three times higher than it was last September.
The level of debt built up is even more worrying as households that pay by monthly direct debit are usually in credit at this time of the year, given gas usage is much lower in the summer.
The Uswitch survey found almost a quarter of households - equivalent to six million homes – currently owe an average of £206 each to their energy provider, 10% more than at the end of last winter.
The findings come with just over two weeks to go until energy regulator Ofgem is due to announce how much it will hike its price cap for 24 million households from October 1.
Consultants Cornwall Insight yesterday predicted the cap for a typical standard tariff customers would leap from £1,971 a year to £3,582 in the autumn.
The new estimate is over £200 higher than it was forecasting just a month ago and follows a further rise in wholesale energy costs and changes Ofgem announced recently.
Cornwall Insight is now predicting the price cap will jump to an average £4,266 in January - over £650 more than it was previously estimating - then £4,426 a year next April.
That would mean prices will have rocketed by 124% in the space of just 12 months.
Justina Miltienyte, head of policy at Uswitch.com, said: “Energy debt has hit an all-time high with the worst possible timing, turning this winter’s energy price hike into a deeply precarious situation for many households.
“Our data shows that while a similar proportion of people are in debt as in April - people now owe approximately 10% more than just four months ago to their energy suppliers.
“This is an alarming situation, as summer is traditionally a time when households are using less power for heating, which helps bill payers to build up energy credit ahead of the winter.”
Craig Lowrey, principal consultant at Cornwall Insight, said: “The cost-of-living crisis was already top of the news agenda as more and more people face fuel poverty - this will only compound the concerns.”
Campaigners now fear 9.2 million households - over 28% - will be left in fuel poverty from October, even with the help already announced by the government.
That could rise to 10.5 million households from January - or 32.6% of all households.
Simon Francis, co-ordinator of the End Fuel Poverty Coalition, said: “A tsunami of fuel poverty will hit the country this winter and these latest estimates further demonstrate that the level of support already promised by the government is just a drop in the ocean.”
Morgan Wild, head of policy at Citizens Advice, said: “The cost-of-living crisis is already having a devastating impact on people’s lives.
“Every day we hear from people who can’t afford to turn the lights on or cook their kids a hot meal.
“The government did the right thing by bringing in targeted support, but it won’t be enough for people to manage these previously unthinkable price hikes.
“The obvious place to start is to increase benefits to keep pace with the cost of living. “There’s no time to waste.”
The latest warning, and concerns over soaring debts, come amid criticism of the Tory government for failing to announce new emergency help for cost of living ravaged households.
Liberal Democrat leader Ed Davey has called on the government to recall Parliament to pass a law to scrap the energy price rise as soon as possible.
He said: “People are worried sick about the next staggering rise in energy bills which is just round the corner.
“Yet we are faced with a deafening silence from the Prime Minister and Chancellor, while both Conservative leadership candidates have failed to come up with a bold plan to solve this crisis.”
