Labor will call on Monday to freeze the energy price ceiling at its current level of £1,971 as UK households struggle to pay their bills.
The move to block an expected raise 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 purchasing power by three times as much as high-income households to pay their energy bills this winter.
Labor leader Sir Keir Starmer will call for a price ceiling freeze in a speech, pitching how his party will pay for the measure, The Observer said.
Specific information on the measure was not available, although Sir Keir wrote elsewhere that the party sought to end the “injustice” in the energy field.
“We would end the injustice that sees people paying for their energy on prepayment meters,” he wrote in The Sunday Mirror.
“And we will map out in the coming days how we are going to help people directly this winter.”
It comes after Sir Keir said on Friday it was “nonsense” to claim his party has not taken the lead in the cost of living crisis.
Last week, the party announced it wanted to end the “outrageous” premiums faced by prepayment meter customers.
Shadow Chancellor Rachel Reeves said Labor would end the “unjustified” practice that could lead to people with energy prepayment meters being charged more than those who pay by direct debit.