Liz Truss has cancelled a scheduled interview on the BBC with just a week to go before the next Conservative Party leader is announced.
A BBC spokesperson said: "Liz Truss has cancelled her BBC One interview with Nick Robinson which was due to air this Tuesday evening (30 August) at 7pm.
"Ms Truss's 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 10 August.
"We regret that it has not been possible to do an in depth interview with both candidates despite having reached agreement to do so."
A source from Ms Truss's campaign told the PA news agency she is not participating in the interview as she is focused on winning as many votes as possible and on preparations for government.
But Mr Sunak's team suggested that Ms Truss is avoiding "proper scrutiny" as she "doesn't have a plan" to help people manage their soaring energy bills.
A source from the former chancellor's campaign said: "Its important that candidates face proper scrutiny so that members and the public know what they are offering.
"Avoiding that scrutiny suggests either Truss doesn't have a plan at all or the plan she has falls far short of the challenges we face this winter."
Labour shadow minister Conor McGinn added: "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."
Mr Robinson said he was "disappointed and frustrated" that his interview with Ms Truss had been cancelled.
The winner of the leadership race - and next prime minister - will be announced on 5 September.
The contest was triggered after Boris Johnson was forced to resign following a number of scandals.
Foreign Secretary Ms Truss has been widely tipped as the frontrunner for much of the race.
The final Tory leadership hustings will take place this Wednesday in London.
The victor will face growing pressure to announce further support to get households and businesses through the cost of living crisis as soon as they get the keys to Number 10.
It follows Friday's announcement from Ofgem that the energy price cap would rise by 80% come October, leading to the average household paying £3,549 a year for their gas and electricity.
Mr Johnson has insisted it is up to his successor to decide what action to take.
A government spokesperson said the Civil Service is "making the appropriate preparations in order to ensure that any additional support or commitments on cost of living can be delivered as quickly as possible when the new prime minister is in place".
Earlier on Monday, former Conservative cabinet minister Rory Stewart said Mr Johnson could try to force his way back into office.
Mr Stewart - who stood against the PM for the Tory leadership in 2019 - told the BBC Mr Johnson was a "terrible prime minister".
He likened the PM to former Italian premier Silvio Berlusconi and ex-US president Donald Trump who are both plotting comebacks.
Mr Stewart also accused the outgoing prime minister of having "an extraordinary ego" and said Mr Johnson "doesn't see the reality, which is he was a terrible prime minister and that he lost his job because of deep flaws of character".
"I fear we are going to end up with a second [Silvio] Berlusconi or a second [Donald] Trump trying to rock back in again," he continued.
Meanwhile, polling has suggested Conservative voters would choose Mr Johnson to stay on over either candidate if they had the chance.