Some Universal Credit claimants face spending more than half their money on energy bills from January if no more help is announced.
Labour warned a single, childless claimant will spend 59% of their cash on electricity and gas from January when bills are projected to top £4,200 a year. From October to December the figure is 42%.
Couples with children would also be spending 24% of their payments on energy bills from October, Labour said.
Shadow Work and Pensions Secretary Jonathan Ashworth said: “Low-income families are set to have their finances devastated by the Tories’ inaction on skyrocketing energy prices.
“People receiving Universal Credit – including those who are in work, or cannot work because of sickness and disability – cannot afford any more delay from this zombie government.”
Labour looked at DWP statistics which said the average UC payment to single adults is £540 a month and to couples with kids is £1,050.
Labour also factored in the Tories’ £400 bills discount, spread over six months from October to March, and a £324 cost of living payment to benefit claimants by Christmas.
But the party weighed that against a predicted bills rise to £3,582 a year from October and £4,266 from January.
A Government spokeswoman said vulnerable families were getting “at least £1,200 of direct payments” including a £326 payment in July, which Labour did not factor in to the figures.
Labour did not include the £326, arguing that because it was paid in July, it was timed to cover the period before winter kicks in.
The party also did not factor in the £326 payment when considering bills from January, arguing it will have been eaten up by then as they are paid every three months.
Boris Johnson has already promised his successor will do more and Liz Truss and Rishi Sunak have both spelt out some plans to do so, though they face calls to go further on detail.
The government spokeswoman added there was a £37bn support package including a £330 a year tax cut, people on Universal Credit can keep £1,000 more of what they earn, and crisis families can turn to a Household Support Fund boosted by £500m.
