Rishi Sunak has lashed out at Liz Truss's economic plans, warning she could pour "fuel on the fire " with her controversial tax cuts.
Speaking ahead of a hustings event in Birmingham, the former chancellor warned that the leadership favourite could cause spiralling inflation if she takes office.
It is the latest blue-on-blue attack as the cost-of-living crisis deepens, with questions over Ms Truss's response to the misery facing millions of Brits.
Mr Sunak, speaking to broadcasters ahead of the hustings, said he understood tax cuts "may sound attractive at first, but if they risk stoking inflation and actually do nothing to help poorer people and pensioners, then they actually are going to be bad for everyone".
"I think people know if something sounds too good to be true, it probably is," he said.
Pressure is mounting on the government to respond to the cost-of-living crisis, with households potentially facing bills of more than £100 a week by the spring.
Mr Sunak said: "I'd cut VAT on energy bills to provide some support to everyone, but I want to provide direct financial assistance to two other groups of people - those on the lowest incomes and pensioners, because those people will need extra help this autumn and winter and I know things are difficult and I want them to be reassured that with me as prime minister, they will get the help that they need."
He also criticised plans to review or look at the Bank of England's mandate on inflation - adding that borrowing money at the moment to fund tax cuts would be a "big gamble".
"I don't want to put fuel on the fire, I don't think that is the right approach."
Polls show Ms Truss is the overwhelming favourite in the race for Downing Street, with the winner set to be announced in a fortnight.
Earlier Mr Sunak's supporter Robert Halfon, appearing on Sky News, insisted the former chancellor would not quit the contest.
The senior Tory MP said: "The contest will be over very shortly. I think it's right that members have a choice. It's still all to play for."
Ms Truss said that rather than focus on freezes to the energy price cap, as Labour has demanded, her administration would "look at the longer-term solutions about how to bring energy prices down".
It came as the chairman of the Treasury Select Committee said he had written to Chancellor Nadhim Zahawi, as well as the Office for Budget Responsibility (OBR) to ask whether work is being carried out to prepare for a potential emergency budget.
Mel Stride, who backed Mr Sunak in the contest, has asked for a response by the end of the week.
He said: "Whether such an event is actually called a budget or not is immaterial. The reassurance of independent forecasting is vital in these economically turbulent times.
"To bring in significant tax cuts without a forecast would be ill-advised. It is effectively 'flying blind'."
