Gordon Brown has urged the Government to temporarily renationalise energy companies that fail to cut bills for their customers this winter.
The former Labour prime minister and chancellor demanded immediate action to ease the financial burden on struggling Britons before Boris Johnson leaves No 10 on September 6.
Mr Brown said decisions including cancelling the expected October energy price cap rise and finding "urgent" new gas and storage supplies must be made in the coming days.
Demanding autumn payments for vulnerable households and a new "watertight" windfall tax on electricity and gas, Mr Brown said the Government should offer guaranteed loans and equity financing to energy companies so they could keep their prices down.
But writing in the Guardian, he added: "If this fails, then as a last resort operate their essential services from the public sector until the crisis is over.
"Time and tide wait for no one. Neither do crises. They don’t take holidays, and don’t politely hang fire – certainly not to suit the convenience of a departing PM and the whims of two potential successors.
"The truth is that without a plan the Government is lurching from one crisis to another, failing to address the anxieties of families who see nothing more than pain now and pain later.
"Churchill once said that those who build the present in the image of the past will utterly fail to meet the challenges of the future."
Mr Brown also warned that families will "suffer more" during the coming months than when Britain was hit by the financial crash and subsequent recession in 2008 and 2009.
It is the latest in a series of high-profile interventions from Mr Brown, who has also called for an emergency Budget before the next prime minister is chosen and daily meetings of the Government’s Cobra committee.
The latter idea was dismissed by Oliver Dowden, the former Tory chairman, who said: "I don’t take enormous lessons from Gordon Brown, remember this was a man who gave us a 75p rise for pensioners, so he’s not really got a great record on this sort of thing."
During an early debate, the Tory leadership front-runner Liz Truss likened her rival Rishi Sunak to Mr Brown, and said his refusal to immediately cut taxes would cause a recession.
Labour is finally expected to set out its stall on the cost of living crisis with a series of proposals next week, although Sir Keir Starmer will reportedly not give a keynote speech on the topic.
Sir Keir this week faced criticism from the Left of his own party for "not demanding nearly enough", as backbencher Zarah Sultana accused him of sending "the wrong signals".