Labour's National Executive Committee (NEC) will today decide if incumbent Jeremy Corbyn will automatically be included on the leadership ballot while rival Angela Eagle has called for his resignation.
Unions, largely supportive of Corbyn, want him on the ballot irrespective of whether he can gain the backing of 51 MPs, against the legal analysis commissioned by Labour.
If it is decided he cannot run, it is anticipated that a legal challenge will be made.
The decision comes after Angela Eagle yesterday launched her bid for Labour leadership, pledging to unite the party.
And this morning the former shadow business secretary, who left her post amid the slew of resignations, told the BBC that Corbyn has "been hiding in his room", adding "he should do the right thing. We need somebody who can persuade now, rather than someone who just protests."
On Sunday Eagle said that Corbyn should not get a place on the ballot without the support of MPs.
"He will have to find nominations. I am ready to have a leadership contest and a debate with whoever’s on the ballot," she said, adding that it was a matter for Labour's National Executive Committee to "set out the terms of this battle".
But it is unlikely that he'd get the support of 50 Labour MPs, with just 40 backing him during the motion of no confidence.
The NEC will meet in London as Corbyn will later address Unite's policy conference in Brighton.
The fear for team Eagle is that if Corbyn is included on the ballot, he will win again due to large levels of support for him among the grassroots.