Former shadow chancellor Mr McDonnell, addressing a virtual Stand With Corbyn rally organised by campaign group Momentum, appealed to members not to leave Labour or launch a “civil war”.
He said: “My appeal is for unity, for clarification that we are all on the same page when it comes to wanting to tackle anti-Semitism and the way that we do that is all of us, we stay in the party – this is our Labour Party.
“Secondly, we have lifted the suspension of Jeremy Corbyn. Thirdly, let’s agree across the whole party to launch a programme of anti-racist campaigning and tackling anti-Semitism wherever it rears its head.”
Ms Abbott, who served as shadow home secretary under Mr Corbyn, said it was “vital” that the former leader was reinstated and warned that his suspension would “not help us win the next election”.
And she said: “The priority right now for everyone in our party is to come together and successfully improve the way that Labour handles racism and anti-Semitism.”
Ex-shadow justice secretary Mr Burgon said infighting “serves no-one but the Tory government”, and former Cabinet Office minister Jon Trickett said he believed Mr Corbyn could be reinstated.
Their comments came after Len McCluskey, the boss of the Unite union, a major financial backer for Labour, warned the suspension was an “act of grave injustice” that could cause a split and doom the party to defeat.
But Labour leader Sir Keir Starmer insisted that there is “no reason for a civil war”.
He told BBC Radio 4’s Today programme: “There is no reason for a civil war, there’s no reason to lean inwards, that is not what I want.
“I want to unite the party – that is the basis on which I ran my leadership campaign, I want to unite the party to stop the faction.”
Sir Keir said Mr Corbyn and his team “knew exactly” that he would warn that any suggestion the issue had been exaggerated could lead to expulsion.
“I’m deeply disappointed in that response from Jeremy Corbyn yesterday, not least because I spoke to him the night before the report to set out how I intended to deal with it,” Sir Keir said.
Mr Corbyn issued a statement to accuse the media and his political opponents of having overstated the scale of the problem and say “I do not accept all” of the EHRC findings.
The EHRC concluded the party was responsible for unlawful acts of harassment and discrimination and found evidence of “political interference” in the complaints process by Mr Corbyn’s office.
The former leader has said he will “strongly contest” the decision to suspend him pending an investigation, which also meant the Islington North MP had the Labour whip removed in Parliament.
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