Sir Keir Starmer will face a Labour leadership challenge next week, former health secretary and rival Wes Streeting has told Sky News.
Speaking on The Cathy Newman Show, Mr Streeting, who has previously said he would put himself forward if a race were triggered, said "we can't go on with this uncertainty" and "will inevitably end up in a contest".
Politics Hub: Follow the latest
Pushed multiple times on whether that would mean a formal challenge next week, he agreed.
Next week could see Andy Burnham back in parliament, if he wins the Makerfield by-election this Thursday.
Mr Streeting said he would "rather the prime minister came to his own conclusion" than be forced from office.
"He says he's going to fight a contest. I would like him to reflect," he added.
"I've left the government. I do have respect for Keir Starmer. I like him personally very much, actually, but I think he's got to reflect on his position."
'I don't think he's listening'
He claimed the prime minister is not heeding the warnings from ex-defence secretary John Healey, who resigned last week, and military chiefs about the need to significantly boost spending on defence.
"In terms of the Labour Party, I don't think he's listening to his cabinet; I don't think he's listening to the parliamentary party, and I don't think he's listening to voters, who only in May sent the Labour Party that extremely humbling message at the ballot box," Mr Streeting added.
Mr Streeting said he is "happy to work with" fellow rival Mr Burnham but hinted he won't do a deal with the Manchester mayor not to stand against him should he win a return to parliament later this week.
"I do think that we need a contest," he said.
"I think it's got to be a battle of ideas, not just personalities. I intend to be in that contest."
Mr Burnham has indicated he intends to run for the leadership if he wins in Makerfield, while Mr Streeting has claimed to have the backing of the 80 MPs needed to trigger a challenge.
(c) Sky News 2026: Starmer rival predicts when leadership challenge will happen
What we know about Russian warship that fired warning shots in English Channel
The US-Iran agreement: Breakthrough or bluff?
Trump's gone rogue and left Netanyahu a horrendous choice
Why Ukraine could now have fresh hope of vital US support
Brexit has damaged Britain and Farage knows it, claims minister
Teen charged over White House UFC show attack plot
Naomi Campbell asks for 'respect' at hearing to appeal her charity ban
Social media ban would have stopped me quitting, says Jess Phillips
Russian artist who criticised Putin shot dead near home in Poland