Allies of former Labour leader Jeremy Corbyn have urged party members who are angry about his suspension not to quit the party.
Ex-shadow chancellor John McDonnell joined Unite union boss Len McCluskey in calling for unity, as they argue for the decision to be overturned.
Some members have publicly declared their intention to quit over the treatment of their former leader.
But the move has been backed by others, including former party members.
The party suspended Mr Corbyn over his reaction to a report saying Labour had broken equality laws over its handling of anti-Semitism allegations.
He is facing an internal inquiry over the comments, in which he acknowledged the problems but said the scale of Labour's anti-Semitism issues had been "overstated".
It was this comment that led to his suspension. A crowd-funding page set up to cover any legal costs Mr Corbyn may face has raised over £350,000.
During an online event on Friday evening hosted by Momentum, the left-wing campaign group, several former shadow cabinet members and allies of Mr Corbyn spoke out against the decision to suspend him.
Mr McDonnell said the decision "must be reversed," but the "way we do that is to stay in the Labour party," adding "civil war" would not help the party's cause.
Equally, former shadow Cabinet Office minister Jon Trickett said the move was "unjust," but called for members to "make our stand today and not walk away" - and former shadow home secretary Diane Abbott called for members to "come together" to fight the suspension.
Sir Keir Starmer, who was elected to replace Mr Corbyn as leader in April, said he had been "disappointed" by his predecessor's response to a highly critical report by the Equality and Human Rights Commission (EHRC) on the handling of anti-Semitism complaints.
Defending Mr Corbyn's suspension, Sir Keir told BBC Radio 4's Today programme: "I made it clear the Labour Party I lead will not tolerate anti-Semitism, neither will it tolerate the argument that denies or minimises anti-Semitism in the Labour Party on the basis that it's exaggerated or a factional row."
Mr McCluskey - one of Mr Corbyn's biggest allies whose union bankrolled the party's election campaigns under his leadership - said the party should be concentrating on implementing the report's recommendations.
He described Mr Corbyn's suspension from the party as a "grave injustice" but added that he hoped the issue can be resolved - and urged members angry about it to remain in the party.
"We need the party to be united. Working people out there need us, need a Labour government," he said.
Is this the calm before the storm?
The talk from those backing Jeremy Corbyn has been of discussion, of "resolving" the issue of his suspension for the sake of party unity.
Sir Keir Starmer has been clear he is holding firm on the commitments he has made on anti-Semitism and that he is not going to get personally involved in the disciplinary complaint.
Unsurprising really, given that not 24 hours beforehand the party was found to have breached equality law because staff in the previous leader's office did just that.
This seems to leave little option but to let a formal disciplinary process run its course.
On the one hand, that sends a strong signal from Sir Keir that the party has listened and learnt on anti-Semitism and that nobody is above the process.
On the other, that potentially means weeks of unrest within the party which could threaten to blow up into another big, divisive row at any moment.
Not quite the "line in the sand" then that the Labour leader had hoped for.
Many have used social media to share their intention to end their membership subscriptions, including Andrew Cassidy, 44, from near Glasgow, who has been a Labour member for 10 years.
"The facts, as far as I see them, are that Jeremy Corbyn has shown a lifelong distaste for racism of any bent," he told the PA news agency.
"Being pro-Palestinian is conflated as anti-Semitism, both by the mainstream media and now by Labour Party grandees."
He described Mr Corbyn as "a good man" who had been "hung out to dry in order to distance (Sir Keir) Starmer's Labour from the progressive, inclusive party that Corbyn aimed for".
Another twitter user, Helen Hurd, said: "I have just resigned my membership of the Labour Party as of immediately, I remained a member in the mistaken belief the left needed a voice in the party but I can't do anymore, as a life long supporter I am really upset."
But others on social media said the news had encouraged them to consider joining the party again.
Elliot Cohen, 50, from Hertfordshire told PA that he wanted to rejoin but would wait to see if the EHRC recommendations were implemented.
He added: "Corbyn's suspension - and Starmer's words since his election - are a good start."
And Frances Grey, who left the party in April 2019, told the BBC she had rejoined Labour after Thursday's announcement.
She said Sir Keir had "shown great promise and appears to be doing all the things an opposition party can possibly do and say against a government with an enormous majority.
"Then his action yesterday (Thursday) in expelling Corbyn just gave me even more hope, because he has accepted the role of working to make changes happen, not just to protest about things."
She added that she hoped Sir Keir would "change things" at the next election.
Labour's membership soared under Mr Corbyn's leadership and stood at more than 500,000 at the time of the party's election contest in April.