Labor’s Tom Watson is facing a fresh bid to oust him as deputy leader by abolishing his post.
An initial move was made at the party’s National Executive Committee (NEC) meeting on Friday but it failed to get the two-thirds majority needed.
A further attempt is set to be made on Saturday at the party’s conference.
It is understood the motion was tabled by Jon Lansman, founder of Labor grassroots group Momentum.
The campaign group was set up to support Jeremy Corbyn’s leadership of the Labor Party.
Mr Watson has been at odds with Mr Corbyn over Labor’s stance on Brexit.
He wants another public vote on the UK’s membership of the EU before any general election, but Mr Corbyn has said an election should come first.
The party leader has refused to say which side he might back in a future Brexit referendum under a Labor government.
A Momentum source told the BBC: “We just can’t afford to go into an election with a deputy leader set on wrecking Labor’s chances.
“Labor members overwhelmingly want a deputy leadership election, but our outdated rulebook won’t let it happen.”
Under Labor Party rules, any candidate to challenge the deputy leader must be backed by 20% of Labor MPs and MEPs.
Potential challengers may seek nominations to trigger a deputy leadership election each year prior to the annual party conference.
But nominations which do not gain the 20% threshold will not be taken forward.
The NEC, Labor’s governing body, will vote again on abolishing Mr Watson’s post at the party’s annual conference at 10: 00 BST on Saturday.
Sources told BBC political editor Laura Kuenssberg they expected the vote to be passed.
There will then be a vote on the conference floor in the afternoon, where the bid could be approved, ousting Mr Watson.
BBC political reporter Jessica Parker said Mr Watson’s supporters were “not overly optimistic” that he will win Saturday’s vote.
By Jessica Parker, political reporter
) Conferences are supposed to be a chance for a party to showcase its policies and portray unity – especially when a general election could be around the corner.
But the news of this effort to oust Tom Watson – by abolishing the job he was elected to – has sparked a spectacular clash as members gather in Brighton.
A “farcical distraction”? Needlessly “self-destructive”? That’s certainly what some infuriated Labor MPs think.
But it’s also true to say that Tom Watson has his fair share of critics. Those who think that the deputy has repeatedly undermined the leader, not least by straying on Brexit policy.
So is Tom Watson’s downfall imminent? Not quite. A lot could yet happen – and even those who aren’t keen on the current deputy might wonder whether this is the best way to kick off the Labor Party Conference.
A number of Labor MPs, including former leader Ed Miliband, have condemned the bid to oust Mr Watson.
Hetweetedthat those who had come up with the idea to abolish the deputy leader post had “taken leave of their senses”.
Neither Mr Corbyn nor Mr Watson were at Friday’s NEC meeting.
A senior Labor source said: “Tom had given his apologies to the NEC. .. as he had to look after his children.
“Usually when you disagree within parties on issues like taking a remain stance on Brexit, you have a debate. Seems that in Jeremy Corbyn’s Labor Party they’d rather abolish you than debate with you. “
The position of deputy leader has existed within the Labor Party, which was formed in 1900, for nearly a century.
John Robert Clynes became the first deputy leader in 1922, and the position has since been held by prominent Labor figures including John Prescott and Harriet Harman.
Labor MP Wes Streeting said in a Twitter post the push to oust Mr Watson “isn’t just outrageous, it’s self destructive”.
“Labor Conference this week needs to put the party on a general election footing – talking to the country about our vision for Britain, “he wrote.
Labor MP Jess Phillipstweeted:“Wish that we could just stop pretending & say what we think … There’s a desperate attempt to control & expel anyone who has an
“I’m so sick of pretending just say you hate Tom Watson just be honest.”