Jeremy Corbyn is set to address the remaining Labour MPs amid bitter recriminations over party's catastrophic General Election defeat.
MPs are returning to Westminster with the party in turmoil following its worst election performance since 1935.
Some furious MPs and defeated candidates have angrily pointed the finger of blame at Mr Corbyn, saying his past record and left wing policies were poison on the doorstep.
But allies of the Labour leader have said divisions within the party over Brexit proved impossible to bridge while he was "demonised" by the media.
Mr Corbyn has said he will stand down following a "process of reflection" – with a new leader expected to be in place by the end of March.
However, that is unlikely to lessen the anger when he addresses the Parliamentary Labour Party at Westminster on Tuesday.
Meanwhile, shadow education secretary Angela Rayner is reported to have agreed to step aside in the leadership race to support her close friend, Rebecca Long-Bailey.
The shadow business secretary – a protege of shadow chancellor John McDonnell – has long been seen as the favourite of the left to succeed Mr Corbyn.
Ms Rayner, who had also been touted as a possible contender, was reported to be considering a run for deputy leaders instead.
Other potential candidates include shadow Brexit secretary Sir Keir Starmer, shadow foreign secretary Emily Thornberry and the backbenchers Lisa Nandy and Jess Phillips.
In a sign of the bitter divisions opened up with the party, Ms Thornberry was embroiled in an extraordinary war of words with former MP Caroline Flint.
The shadow foreign secretary threatened to take legal action after Ms Flint – who lost her Don Valley seat – accused her of branding Leave voters as "stupid".
In a weekend TV interview, Ms Flint said Ms Thornberry had told a colleague after the 2016 referendum, "I'm glad my constituents aren't as stupid as yours".
Ms Thornberry said: "One of my former colleagues came out and said the most extraordinary lies about me.
"I've contacted her and I've said to her, 'Please withdraw, I will give you until the end of the day' and she hasn't. So I've had to go to solicitors."