Labour’s Tom Watson has said the bid to oust him as deputy leader by abolishing his post is a “sectarian attack” on the party’s “broad church”.
He told the BBC he found out late on Friday in a text message that a motion had been tabled by Jon Lansman, founder of Labour grassroots group Momentum.
Members had voted him in and should be able to vote him out, he said.
Mr Watson has been at odds with leader Jeremy Corbyn over the party’s stance on Brexit but said he had to speak out.
An initial move to oust him was made at a meeting of the party’s National Executive Committee (NEC) 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 in Brighton.
Speaking to Radio 4’s Today programme, Mr Watson said he found out about the move while having a meal at a Chinese restaurant in Manchester on Friday night.
He called it a “straight sectarian attack on a broad church party, moving us into a different kind of institution”.
He said he felt that Mr Lansman “and his faction” were so angry about his position on Brexit they would “rather abolish me than have a debate about it”.
Asked if he thought the move had been made by Mr Corbyn himself, Mr Watson said “I don’t know”, but added his leader had the power to stop it.
Mr Watson has urged Labour to “unequivocally back remain” and had said he wants another public vote on the UK’s membership of the EU before any general election.
But Mr Corbyn wants to hold another referendum once Labour has won power, in which voters would have the choice to remain in the EU alongside a “credible” Leave proposal.
A Momentum source told the BBC: “We just can’t afford to go into an election with a deputy leader set on wrecking Labour’s chances.
“Labour members overwhelmingly want a deputy leadership election, but our outdated rulebook won’t let it happen.”
Dawn Butler, shadow women and equalities secretary, said Momentum’s move had “come out of the blue” but she could understand the frustration with the deputy leader.
Asked if Mr Watson was doing the job well, she said: “I have my frustrations with Tom too. I haven’t seen him at a shadow cabinet meeting for a while.”
The NEC, Labour’s governing body, is set to vote again on abolishing Mr Watson’s post at the party’s annual conference at 10:00 BST on Saturday.
There will then be a vote on the conference floor in the afternoon, where the bid could be approved, ousting Mr Watson.
BBC political editor Laura Kuenssberg says Momentum’s move “was not discussed” among its governing body – adding there was “anger” at Mr Lansman as this was “not an official decision”.