Shadow education secretary Angela Rayner is to step aside and support her friend Rebecca Long-Bailey to succeed Labour leader Jeremy Corbyn, according to reports.
Ms Rayner is expected to run as deputy leader in a bid that would allow her flatmate, shadow business secretary Ms Long-Bailey, to take the party’s top job.
It comes as Mr Corbyn indicated he would quit as Labour leader in the early part of next year after the party suffered its worst General Election defeat since 1935.
Tom Watson stepped down as deputy leader shortly before the election was called.
According to multiple reports, Ashton-under-Lyne MP Ms Rayner has not made a final decision, but is exploring a deputy leadership bid.
In a tweet on Monday evening , Ms Rayner said she will work “day and night” to restore the party to its “rightful place”.
Ms Long-Bailey, who is the MP for Salford, is one of several candidates said to be a possible successor to Mr Corbyn, having received the backing of senior figures in the party’s current leadership.
It is understood Mr Corbyn will address his much diminished parliamentary Labour party in Westminster on Tuesday, where he will likely face disgruntled MPs.
The Labour leadership battle descended into acrimony on Sunday after another contender, Emily Thornberry, was accused by former MP Caroline Flint of labelling Leave voters “stupid” following the European referendum result in 2016.
Shadow foreign secretary Ms Thornberry accused Ms Flint, who lost her Don Valley seat in the election, of spreading the “most extraordinary lies” and confirmed she had approached her solicitors over the remarks.
Ms Flint accused Ms Thornberry of telling a colleague after the 2016 referendum, “I’m glad my constituents aren’t as stupid as yours” and said the comments were “not acceptable”.
The Islington South and Finsbury MP, speaking on Sky News on Monday, said she had asked Ms Flint to rescind the comment before she started legal action.
“One of my former colleagues came out and said the most extraordinary lies about me,” Ms Thornberry, who is also considered a candidate in the Labour leadership race, said.
“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. I mean, people can slag me off – so long as it is true, I’ll take it on the chin.”
Labour’s general secretary, Jennie Formby, reportedly wrote to the party’s ruling National Executive Committee recommending the contest starts on January 7, with the view of having a new leader by the end of March.