Liz Truss has pulled out of a BBC One interview with Nick Robinson that was due to air on Tuesday evening.
Ms Truss’ team said she could no longer spare the time for the one-on-one programme, the BBC said in a statement.
Rishi Sunak, Ms Truss’ rival for the Conservative leadership, was interviewed by Robinson on 10 August.
The ballot of Tory party members closes on Friday, with the winner set to be announced next Monday, 5 September.
In its statement, the BBC added: “We regret that it has not been possible to do an in-depth interview with both candidates, despite having reached agreement to do so.”
Robinson said on Twitter he was “disappointed and frustrated” that his scheduled interview with Ms Truss – widely considered to be the front-runner to become prime minister – had been cancelled.
Both Ms Truss and Mr Sunak have taken part in a series of hustings across the country, as well as television debates that have included direct questions.
They have faced particular scrutiny over their economic plans amid a growing cost-of-living crisis.
Foreign Secretary Ms Truss has so far committed to cutting National Insurance and axing green levies on energy bills.
Former chancellor Mr Sunak, meanwhile, has proposed cutting VAT on energy bills as part of a £10bn package.
In his interview with Robinson, Mr Sunak said he would rather lose the contest than win it “on a false promise”.
