She is expected to pledge to reunify the fractured party, which has been locked in a vicious internal battle since the weekend, when Corbyn sacked his shadow foreign secretary, Hilary Benn, for plotting against him.
“We’ve got the numbers, we’ve got the big hitters, it will probably be [Thursday] afternoon,” said an ally of Eagle, the former shadow business secretary.
Earlier Labour’s deputy leader, Tom Watson, became the most senior party figure to call on Corbyn to resign, intensifying the pressure on the embattled leader on a day of drama in Westminster.
“It’s a great tragedy,” Watson told the BBC . “He does have a members’ mandate, but those members who join a political party know that you also need a parliamentary mandate if you are to form a government.
“You have to have the authority of the members and your members of parliament, and I’m afraid he doesn’t have that with our MPs.”
Watson said he would not stand in any leadership election himself, apparently clearing the way for Eagle to mount her challenge.
However, Eagle’s local members may oppose her candidacy. The deputy chair of the Wallasey constituency Labour party, Paul Davis, told BBC North West Tonight: “Jeremy Corbyn hasn’t been given a chance to be a good leader.
“If you are being stabbed in the back all the time by your own people on the Labour benches it’s very hard to get your message across. So yes, I do think he’s a good leader.”
Watson said he had attempted to discuss the leadership issue with Corbyn, after his predecessors Gordon Brown and Ed Miliband added their voices to those calling for him to go, but the Labour leader had refused to engage in conversation about his future.
“I’m afraid Jeremy was not willing to discuss that with me,” he said. “I’m assuming that he remains in office. That’s where the situation stands.”
In other developments on Wednesday:
- The Scottish first minister, Nicola Sturgeon, held a series of meetings in Brussels to press the case for Scotland’s continued membership of the EU.
- EU leaders agreed a joint position on the Brexit vote, saying Britain should notify them of its intention to leave as soon as possible after a new prime minister was in place. They insisted the UK has no prospect of keeping access to the single market unless it continues to accept EU migration.
- The work and pensions secretary, Stephen Crabb, was forced to defend his previous opposition on same-sex marriage as his bid for the Tory leadership got off to a rocky start.
- Arron Banks, the Brexit movement’s biggest financial donor, has said he is considering backing a new political party.
Earlier, Corbyn’s spokesman insisted that he would stand again if challenged, and would expect his name to appear automatically on the ballot.
Watson said: “I just think he feels very strongly that he has that mandate from the members. He holds less weight on parliamentary politics, and that’s where he is.
“He’s obviously been told to stay by John McDonnell [the shadow chancellor] and his team, and they’ve decided they’re going to tough this out. It looks like the Labour party is heading for some kind of contested election.”
Corbyn was also backed by 10 of Britain’s biggest trade unions. In a joint statement they said: “Jeremy Corbyn is the democratically elected leader of our party who secured such a resounding mandate less than 10 months ago under an electoral procedure fully supported by Labour MPs.
“His position cannot and should not be challenged except through the proper democratic procedures provided for in the party’s constitution. We urge all Labour MPs to abide by those procedures, and to respect the authority of the party’s leader.
“The only party that can win for working people is a strong and united Labour party.”
The signatories to the statement included the general secretaries of Unite, Unison, the GMB and Ucatt.
Speculation was rife among Labour MPs in Westminster that Corbyn was close to crumbling, after days of resignations and acrimony, and a vote of no confidence in which more than 80% of his MPs withheld their support. All 20 of Labour’s MEPs signed a letter calling for Corbyn to go.
But McDonnell said Corbyn would fight on and denied rumours that he was trying to persuade him to stand down. “Jeremy’s well up for it, he’s enjoying it,” he said.
He added that he expected Eagle to stand at some point in the future, but speculated that there may be some problem in filing the necessary papers because of infighting among Corbyn’s opponents.
“I will continue to support Jeremy. We have been friends for 30 years; if he stands again, I’ll be his campaign manager,” McDonnell said.
Later at a pro-Corbyn rally in London on Wednesday evening, McDonnell described Monday’s parliamentary Labour party meeting at which the leader was urged to resign as “a lynch mob without a rope”.
“MP after MP urged Jeremy to resign on the basis that we could not win an election with him in office,” McDonnell said. “The irony is we were welcoming the winner of the Tooting by-election who doubled her majority.
“They used the referendum as a chance to mount a coup. What is happening is a very British coup going on. But I’ve been trying to explain to some members of the parliamentary Labour party that there’s an extremely recent Greek invention called democracy. This is a battle for democracy.”
In addition to McDonnell, the 200-strong crowd at the rally at the School of Oriental and African Studies was addressed by members of Young Labour and other students.
One student speaker said they were determined to make it “an annual event” to elect Corbyn back to the leadership of the Labour party, no matter what opposition he faced. Though the crowd were mostly students, there were older people as well as a family with young children holding pro-Corbyn banners.
Corbyn’s backers will now hope to win the argument at the national executive committee to have his name automatically included on the ballot paper for any contest, despite the fact that he is unlikely to muster the support of 50 MPs necessary for a candidate to secure a nomination.
The Norwich MP Clive Lewis, a Corbyn backer promoted to shadow defence secretary in the reshuffle held to replace the scores of resigning MPs, said: “I think, speaking to people in the parliamentary Labour party, everyone is desperate for a resolution to this, but I think it’s not acceptable for 170 people to dictate who should be on that ballot paper when there are hundreds of thousands of people who want him on there.”
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