Labor will call on Monday for the energy price cap to be frozen at its current level of £1,971 as UK households struggle to pay their bills.
The move to block a planned rise to £3,300 in October is expected to put further pressure on the two Tory leadership candidates.
A think tank has warned that low-income households will have to reduce their spending power three times more than high-income households to pay their energy bills this winter.
Labor leader Sir Keir Starmer will call for the price cap to be frozen in a speech outlining how his party will pay for the measure, according to The Observer.
Details of the move were not available, although Sir Keir wrote elsewhere that the party aimed to end energy “injustice”.
“We would end the injustice that sees people with pre-paid meters paying over the odds for their energy,” he wrote in The Sunday Mirror.
“And we will outline how we would directly help people this winter in the coming days.”
It comes after Sir Keir said on Friday it was “nonsense” to claim his party had not been leading the charge on the cost of living crisis.
Last week, the party announced it wanted to end the “outrageous” premiums faced by pre-paid energy meter customers.
Shadow chancellor Rachel Reeves said the work would end the “unjustifiable” practice which can result in people with prepaid energy meters being charged more than those paying by direct debit.
