Liz Truss has pledged to make an announcement on energy bills this week if she is named Tory leader.
But she repeatedly refused to say what it will be - and brushed off fears the poorest are facing "Armageddon".
That means millions of Brits facing a plunge into fuel poverty will be holding their breath for days, despite the frontrunner pledging “immediate action on energy bills and energy supply.”
And there are fears her help won't touch the sides - with Ms Truss saying: "Not all of those decisions will be popular but I will be honest about what we will have to do."
Ms Truss - the favourite to be named the next PM at 12.30pm tomorrow and confirmed by the Queen at Balmoral on Tuesday - said her announcement will come before an emergency budget, tipped for September 21.
Yet she refused to say what her help will be - and has spent weeks attacking cash payments as “handouts”.
Grilled by the BBC's new show, Sunday with Laura Kuenssberg, she said: "If I’m elected as Prime Minister, within one week I will make sure there is an announcement on how we are going to deal with the issue of energy bills and of long term supply to put this country on the right footing for winter."
Yet asked repeatedly to say what it'll be, she added: "I’m not going to go into details of what a putative announcement would be before."
Worryingly, she indicated her “precise plans” may have to be overhauled. “Before you have been elected as Prime Minister, you don't have all the wherewithal to get the things done,” she said. “This is why it will take a week to sort out the precise plans and make sure we are able to announce them."
She also appeared to row back on indications she could review the Bank of England's interest-rate setting powers, saying: "I think it would be completely wrong for me as a politician to say what I wanted interest rates to be and to countermand the Bank of England."
Comedian Joe Lycett - who was also on the show - sarcastically said Ms Truss's answers were "very clear".
Labour's Emily Thornberry said people "are desperate", adding: "It's extraordinary that we've had a leadership election that has gone on for weeks and weeks, and yet the two leadership candidates cannot give a specific answer to the one question, frankly, that everybody wants the answer to.
"Which is what the heck is going to happen to my bills? What is going to happen?
"You're going to have the majority of the country in fuel poverty unless something is done."
In a bizarre moment, Ms Truss said her plans to cut National Insurance were "fair" - while confronted with a graph that showed they will give the poorest just £7.66 a year and the richest £1,801.89.
Ms Truss - who has pledged to reverse a rise that happened in April - said: “It is fair. We promised in our manifesto that we would not raise National Insurance.”
In a stark warning she will not always prioritise helping the neediest, she said: “To look at everything through the lens of redistribution I believe is wrong”.
And on the economy more generally she added: "I don't think we should be predicting a sort of Armageddon scenario. I think we are in a good position to deal with what are very very tough challenges."
Writing in the Sunday Telegraph she added: “Sticking plasters and kicking the can down the road will not do. I am ready to take the tough decisions to rebuild our economy.”
Ms Truss said she would appoint a council of economic advisers to help guide her and her chancellor.
And the crisis will be the focus of her “very short” first address from Downing Street on Tuesday after she jets back from Balmoral, the Times reported.
But campaigners, Labour and economists warn her plan to undo National Insurance and corporation tax rises will not touch the sides for the poorest.
Household bills are set to rocket from £1,277 a year last winter to £3,549 a year this winter - and far higher for businesses, who warn they face financial ruin.
And according to The Sunday Times, police are braced for "civil unrest" and rising crime like burglary this winter as cost pressures grow.
Ms Truss wrote in the Sunday Telegraph: "I recognise that many of the growth measures we take won't have an immediate impact.
“But it is vital we get started now and build a better economy for the future and pay down our debt as a country and provide the future for our children.
"There will be tough decisions to be made, and I am prepared to make those tough decisions as prime minister.”
Treasury officials were drawing up options last week including raising Universal Credit and giving more targeted support to vulnerable groups.
Rishi Sunak backer David Davis warned Sky News: “It’s going to be on a par with the furlough scheme, in terms it's going to be tens of billions of costs.
“it's going to be rewriting markets, it's going to be intervening.
“That's what should happen - it has to happen.”
He warned Ms Truss against creating a "Cabinet of loyalists", adding: “There is real risk the party will feel divided and if that’s the case we won't win the next election.”
Scotland's First Minister said Liz Truss will be a "disaster" as prime minister if she governs how she has campaigned.
Nicola Sturgeon told Sky News: "If she governs how she has campaigned over the summer, she will be a disaster - not just for Scotland but for all of the UK.
“But let's hope that's not the case, because this is a very serious time for the UK and it needs very serious and very purposeful leadership."
Ms Truss’ ally and Chief Secretary to the Treasury Simon Clarke wrote in The Sun on Sunday: “She knows that people need help now, and will take decisive and immediate action to this end.
“She will support people in the short term, and fix our economy for the long term.”
And Boris Johnson, in a 1,600-word farewell article in the Sunday Express, added: “I know that both candidates will do even more to help people with the cash they need to pay their bills, in addition to the large sums that are already arriving in the next weeks and months.
“Both candidates will find other ways to ease the pressures on families - such as sensible tax cuts.”
It came as a poll claimed the majority of people who voted Tory in 2019 think Ms Truss is out-of-touch and untrustworthy.
Opinium’s survey rated her at -12% on being “in touch with ordinary people” and -2% on being “trustworthy”.
Meanwhile refugees minister Lord Harrington quit his role - but insisted it was “not a political statement”.
He said: “I'm very pleased to remain as an advisor. I just don't think it needs the seven day a week concentrated political ministerial involvement.”
Ms Truss’ south London neighbour Kwasi Kwarteng is tipped to become her Chancellor while ‘anti-woke’ right-winger Suella Braverman could be made Home Secretary.
There is also a growing expectation that the next prime minister will make an early visit to Kyiv to shore up support for Ukraine.
In what is set to be a frenzied few days for UK politics, Mr Johnson's successor will be announced on Monday, taking over as prime minister the following day.
Mr Johnson and his successor will go to Balmoral, rather than Buckingham Palace, for the appointment of the new prime minister on Tuesday, in a break from tradition.
The Queen will receive Mr Johnson on Tuesday at her Aberdeenshire home, where he will formally tender his resignation.
This will be followed by an audience with the new Tory leader, where she or he will be invited to form a government.