Labour peers are poised to stage a no confidence vote in Jeremy Corbyn's leadership, the Mirror understands.
It is understood an extraordinary meeting of Labour's Peers Group has been scheduled for Monday over Mr Corbyn's response to anti-Semitism claims.
Peers are due to use the meeting to discuss whether to hold a no confidence vote in the party leader. One source said it is "almost inevitable" peers will choose to express their view through a formal vote.
If agreed, a ballot of all 179 Labour members in the House of Lords would then follow on Tuesday and/or Wednesday.
That means the result could come within hours of a new Prime Minister taking office on Wednesday.
It's understood a no confidence vote is currently proposed by one peer, whose identity has not yet been revealed.
While a no confidence vote would not be binding it would heap pressure on the Labour leader over anti-Semitism.
But a source close to Labour's leadership hit out at the move.
They said: "It would be both undemocratic and absurd for unelected peers with no mandate to seek to remove an elected leader who twice won the landslide support of Labour’s membership and led Labour to the biggest increase in the party’s vote since 1945."
It comes after shadow Brexit minister Baroness Hayter was
And accusing him of a "failure of leadership".
A Labour spokesman dismissed the peers earlier this week, saying the advert contained "false and misleading claims about the Party by those hostile to Jeremy Corbyn's politics".
A source said the vote was a reaction to the leadership's general handling of anti-Semitism claims - but critics felt they were pushed over the brink by Baroness Hayter's sacking.
A Labour spokesman said yesterday: " Jeremy Corbyn has made clear in interviews, videos and articles that there is no place for antisemitism in the Party.
"Jennie Formby has sped up and strengthened procedures and the rate at which cases are dealt with has increased more than four-fold. Since September 2015, the number of cases that have undergone disciplinary procedures relate to about 0.06% of members."
It comes more than three years after Jeremy Corbyn lost another non-binding no confidence vote, staged by his MPs, by 172 votes to 40.
Despite the huge margin Labour's leader refused to quit, citing support among the party's 500,000-odd members.
Labour has been engulfed in a storm for more than a week over a BBC Panorama documentary that claimed key aides to Jeremy Corbyn intervened in anti-Semitism cases.
Labour branded the programme misleading and inaccurate, accused former staffers of having "axes to grind", and demanded the show is taken off iPlayer .
But Labour's shadow cabinet will hold an emergency meeting next Monday. And its ruling NEC is set to discuss calls to set up a new independent investigations process following a push by deputy leader Tom Watson.
Meanwhile a proxy row raged after Mr Watson demanded general secretary Jennie Formby answer questions - only for her to slam the deputy leader for "traducing" her reputation while she undergoes cancer treatment.
Labour's shadow Brexit minister in the Lords was last night sacked for comparing Jeremy Corbyn's leadership to "the last days of Hitler".
Baroness Hayter was removed after party chiefs branded the remark "deeply insensitive".
But she was given a hero's welcome in the Lords today - with the chamber erupting into loud cheers on all sides.
She had hit out at the "bunker mentality" of the Labour leadership during the antisemitism crisis, saying in a meeting: “Those of you who haven’t [read the book] will have seen the film ‘Bunker’, about the last days of Hitler, where you stop receiving any information into the inner group which suggests that things are not going the way you want.”
She added: “That seems to be where we are at the moment."
