The favourite to be the next prime minister was due to be quizzed by the BBC’s Nick Robinson on Tuesday evening, but has pulled out because she can “no longer spare the time”.
The decision comes after Ms Truss’s economic plans were strongly criticised by the Institute for Fiscal Studies (IFS), which warned massive unfunded tax cuts would “crash the public finances”.
There is growing confusion over what help the foreign secretary plans to ease the pain of rocketing energy bills – after she first “ruled out” help for every household, but then appeared to rethink the stance.
Ms Truss had already come under fire for refusing to be interviewed by Andrew Neil – regarded as TV’s toughest test for any politician – but then agreed to face Mr Robinson.
Announcing the cancellation, the BBC news department said: “Ms Truss’s team say she can no longer spare the time to appear on “Our Next Prime Minister”.
“We regret that it has not been possible to do an in depth interview with both candidates despite having reached agreement to do so,” it said – referring to Mr Robinson’s interview with Rishi Sunak earlier this month.
A spokesperson for the former chancellor’s campaign said: “It’s important that candidates face proper scrutiny so that members and the public know what they are offering.
“Avoiding that scrutiny suggests either Liz Truss doesn’t have a plan at all or the plan she has falls far short of the challenges we face this winter.”
And Conor McGinn, Labour’s shadow minister without portfolio, said: “People will rightly conclude that she doesn’t want to answer questions about her plans for the country because she simply hasn’t got any serious answers to the big challenges facing our country.”
The race frontrunner has not provided an explanation for the cancellation, which comes with just one party hustings left in the campaign – on Wednesday evening.
It appeared Ms Truss decided that, with every poll pointing to a handsome victory over Mr Sunak next Monday, she had little to gain from the interview, but potentially a lot to lose.
Her only lengthy broadcast interview of the two-month campaign, with BBC Radio 4 in mid-July, kicked off a major row about the credibility of her economic strategy.
She argued her £30bn-plus tax-slashing plans would tame soaring inflation – turning economic orthodoxy on its head.
One economics professor told The Independent the claim was “ridiculous”, while the IFS went further, also highlighting the danger for public services and spending rules.