Sir Keir Starmer is tomorrow expected to call for the energy price cap to be frozen this autumn as households across the UK feel the pinch amid the cost of living crisis.
The Labour leader will say the price cap, which is the maximum that firms in England, Wales and Scotland can charge an average customer for energy costs, should remain at £1,971.
Energy analysts have predicted that typical energy bills could rise to approximately £3,500 in October and more than £4,200 in January.
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And a new report suggests that energy bills are set to cost more than two months of average take home pay next year unless the government intervenes.
Earlier this week, the Liberal Democrats called for the energy cap to be scrapped together.
The government has already announced that households will receive £400 to help pay rising fuel bills in the autumn.
But Boris Johnson admitted on Friday that the current plans do not go far enough as pressures on households continue to mount.
The prime minister also reiterated his insistence that it is for his successor to “make significant fiscal decisions” after talks with energy bosses ended with no new measures to ease the cost of living crisis.
Mr Johnson’s successor will not be announced until 5 September.
The PM added that he would continue to urge the energy sector to ease the financial pressures facing struggling families.
Also speaking on Friday, Sir Keir pledged to lay out his party’s “comprehensive plan” to deal with the costs of living crisis – including rising energy bills – on Monday.
“We do need a strategic, a credible, plan and that’s exactly what’s missing from this government,” he said.
On Thursday, Labour vowed to stop the “outrageous” premiums that energy prepayment meter customers face.
The party says the prepayment meter policy would help to bring prepayment energy prices into line with those for direct debit customers, and estimates that it would provide relief to four million households.
It is thought that Labour would remove the gap between the two price caps and reimburse energy companies for the difference between October and March – at an estimated cost of £113m.
Labour says this would be paid for by a strengthened windfall tax on oil and gas companies.
A spokesperson for the Department for Business, Energy and Industrial Strategy said: “Pre-payments meters remain an effective way for people to pay for their energy use whilst managing costs and debt, while the energy price cap protects four million pre-payment meter customers from overcharging by energy suppliers.”
Sir Keir added that: “For the best part of 12 months, Labour has been absolutely leading on this issue.”
The Labour leader has received criticism, along with Mr Johnson, for taking a holiday at a time of national crisis.
Earlier in the week, shadow justice secretary Steve Reed denied that Gordon Brown was leading the party’s policy in Sir Keir’s absence after the ex-PM called for energy firms to be temporarily nationalised, in his third major intervention this week.
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It is expected that both Labour’s proposal to freeze the energy price cap for the autumn months and how it will be paid for will be unveiled by Sir Keir on Monday.
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Also speaking on Friday, Chancellor Nadhim Zahawi said options to provide additional help to people to ease cost of living pressures will be “ready to go” on 5 September – but, like Mr Johnson, added that it will be up to the new prime minister to take decisions on the matter.
Tory leadership hopeful Mr Sunak has unveiled a plan to slash rising energy bills for up to 16 million vulnerable people which he hopes will propel him to 10 Downing Street.
The ex-chancellor has also said he would legislate to make the UK “energy independent” by 2045, and put in place immediate support for households – particularly the most vulnerable – faced with soaring energy bills.
And he has vowed to drive up domestic energy supply with the creation of a new energy security task force and deregulation in the North Sea to allow gas production to increase over the winter.
Meanwhile, fellow leadership candidate Liz Truss has said cutting taxes is the best way to help with living costs over winter.
But the foreign secretary has dismissed calls for a windfall tax on oil and gas firms’ profits.