Labour peers are to hold an emergency meeting next week to consider a motion of no confidence in Jeremy Corbyn.
The move comes after frontbencher Baroness Hayter was fired for comparing the “bunker mentality” around Mr Corbyn’s leadership to the “last days of Hitler”.
A source told PA peers will meet on Monday afternoon to discuss the motion, with a ballot to be held on Tuesday or Wednesday if it is passed.
The move would not be binding but would heighten pressure on the leadership, which has been heavily criticised over the party’s handling of anti-Semitism allegations.
On Wednesday, Baroness Hayter lost her post as shadow Brexit minister after she attacked Mr Corbyn’s inner circle and the way it criticised the BBC over a documentary probing anti-Semitism in the party.
A Labour Party spokesman said: “Dianne Hayter has been sacked from her frontbench position with immediate effect for her deeply offensive remarks about Jeremy Corbyn and his office.
“To compare the Labour leader and Labour Party staff working to elect a Labour government to the Nazi regime is truly contemptible, and grossly insensitive to Jewish staff in particular.”
The row erupted over an address given by Baroness Hayter, who remains Labour’s deputy leader in the Lords because it is an elected position, to a party fringe group.
The peer was highly critical of the Labour leader’s inner circle, which she claimed had refused to give the party’s ruling National Executive Committee key information.
Baroness Hayter said those around Mr Corbyn had a “bunker mentality”.
She told the meeting of the centre-left Labour First group: “Those of you who haven’t [read the book] will have watched the film ‘Bunker’, about the last days of Hitler, of how you stop receiving into the inner group any information which suggests that things are not going the way you want.”