Keir Starmer will make a major intervention in the energy crisis on Monday by calling for a price cap freeze.
The Labour leader, who has been accused of being too quiet over the cost of living crisis, will call for the cap to be frozen at its current level of £1,971.
His plan would block an expected increase to £3,300 in October and will put pressure on the the two Tory leadership contenders.
Both Liz Truss and Rishi Sunak have been criticised for not putting their heads together with the outgoing administration to come up with a plan to help struggling households pay their bills.
Starmer will call for the price cap freeze in a speech in which he will pitch how his party will pay for the measure, according to The Observer.
Specifics of the measure were not available, though Starmer wrote elsewhere that the party aimed to end energy “injustice”.
“We would end the injustice that sees people on prepayment meters paying over the odds for their energy,” he wrote in The Sunday Mirror.
“And we will set out how we would help people directly this winter in the coming days.”
It comes after Starmer on Friday said it is “nonsense” to claim his party has not been leading on the cost-of-living crisis.
Last week the party announced it wanted to put a stop to “outrageous” premiums that energy prepayment meter customers face.
Shadow chancellor Rachel Reeves said Labour would end the “unjustifiable” practice that can result in people with energy prepayment meters being charged more than those who pay by direct debit.
A think tank has warned households on low incomes will have to reduce their spending power by three times as much as high income households in order to afford their energy bills this winter.
It has already been announced by the government that all households in England, Scotland and Wales will receive £400 to help pay rising fuel bills this autumn.
But ministers have been accused of going “missing in action” amid the worsening picture with the government paralysed by the race to replace Boris Johnson.
Remaining ministers are said to be working on a new cost of living package that will be put to the next prime minister.
Truss, frontrunner in the race, has declined to sit down with her rival to discuss a plan. Meanwhile, Downing Street has said Johnson would not make any major fiscal interventions.
Sunak said he would offer specific support to pensioners and those on benefits, while Truss has promised several tax cuts, including on national insurance contributions and green levies on energy bills.