Liz Truss's tax-cutting plans would "completely crash the public finances", an influential economist has warned.
Institute for Fiscal Studies boss Paul Johnson blasted the Tory leadership frontrunner for pursuing a "simplistic" bid to solve the cost of living crisis by slashing taxes - and said the ideas bandied about were "quite worrying".
Earlier, Labour former Chancellor Alistair Darling warned that rocketing inflation coupled with a looming recession could generate a “lethal cocktail” to the British economy.
Lord Darling, who led the Treasury during the 2007/8 financial crisis, urged ministers to go harder and faster on plans to ease the misery for families.
It comes as Ms Truss pulled out of a BBC interview with Nick Robinson saying she "doesn't have time".
The interview was supposed to air on Tuesday evening at 7pm and Mr Robsinon has since said he's been left "disappointed and frustrated" that she pulled out.
Ms Truss is understood to be focusing on tax cuts and boosting productivity, before looking at what further support is needed for households facing a cost of living catastrophe this autumn.
The likely next PM is said to be considering slashing VAT by 5% - which could cost £39billion - as well as income tax cuts, as she prepares for victory in the Tory leadership race.
Ms Truss has already vowed to axe the National Insurance hike that came into effect in April and to scrap a planned rise in corporation tax.
Her team insist she isn't ruling anything out but she has signalled her reluctance to offer immediate direct support to households - such as the £400 energy bills discount Brits will receive this autumn.
Mr Johnson said her VAT cut idea was "inappropriate" and questioned the need for slashing income tax on top of other measures.
He told The Times: "You clearly can’t do all of this without completely crashing the public finances.
“This simplistic mantra that you cut taxes and the economy grows more, that you cut taxes when you have a big deficit and high inflation, and you don’t do it with any other part of the plan, is quite worrying.”
He said her plans to slash the green energy levy on bills were "between meaningless and pointless" and would save households just £11 over three months.
Mr Johnson said the new PM must choose to either "substantially step up the packages that have been put in place already — increasing the universal £400 off energy bills and the extra support to pensioners and benefit recipients — or do something even more dramatic".
He branded Labour calls to freeze energy bills as "extraordinarily expensive and substantially wasteful" and warned it was "dangerous" for the Government to start subsidising energy bills.
Earlier today, the BBC, tweeted: "Liz Truss has cancelled her BBC One interview with Nick Robinson which was due to air this Tuesday evening (30th August) at 7pm. Ms Truss’ team say she can no longer spare the time to appear on “Our Next Prime Minister".
"The other candidate for the Conservative leadership, Rishi Sunak, was interviewed by Nick on 10th August.
"We regret that it has not been possible to do an in-depth interview with both candidates despite having reached an agreement to do so."
Mr Robsinon later tweeted: "Was pleased to secure an in-depth interview with @trussliz on BBC1. I am disappointed & frustrated it’s been cancelled."
The Government has been paralysed as energy bills soar, prices spiral and real wages are hammered, as Tory leadership hopefuls Liz Truss and Rishi Sunak battle to succeed lame-duck Prime Minister Boris Johnson.
Labour big beast Lord Darling said: "You need something significant and substantial and you need it now, because people's bills are going to start coming in in a few weeks time.
"If you don't do that then you have the risks … that the economy will slip into recession with all that entails - and when you've got that on top of the fact you've got inflation already at very, very high levels we haven't seen since the 1970s.
"This is a lethal cocktail, which is why it needs bold action taken by the Government now, not fiddling around with small measures that frankly won't make any difference at all."
The peer said he learned during the financial crisis that acting sooner and more forcefully was key to easing the chaos.
"One lesson that I drew from what happened in 2008 is you've got to do more than people expect and you've got to do it more quickly than people expect if it's going to work," he said. "It's going to cost money.”
He added: “What I think we need to see today from the Government, from the new prime minister, is measures that will be big enough to deal with this.”
Rubbishing previous measures to help hard-up families, he went on: "Frankly, the stuff that's been announced so far might have passed muster earlier this year. It simply won't do now.
"You need something far more substantial than that unless you are willing to see substantial damage being done to our economy."
Former British diplomat Peter Ricketts accused the Government of “drifting over the last two months.”
He hailed the “very ambitious proposals” of other world leaders to tackle the crisis.
Government minister Victoria Prentis claimed: "It's right that people need help and I'm really here to try to reassure that the Government is making plans to help people as they will need it with energy bills this winter.”
