Jeremy Corbyn faces a historic Labour rupture after being warned that more MPs are ready to follow the seven who dramatically quit his party on Monday.
The leader publicly appealed for unity while his supporters launched savage attacks on the MPs, branding them “cowards”, “traitors” and “splitters” and demanding they give up their seats.
But as the crisis deepened, deputy leader Tom Watson said other MPs are also considering leaving Labour, a party he admitted he sometimes no longer recognises, amid visceral anger over antisemitism, Brexit and Mr Corbyn’s leadership.
The breakaway MPs headed by prominent backbenchers Chuka Umunna and Luciana Berger said they would form a new “Independent Group” in the House of Commons and invited people from other parties to join.
There were some early signs on Monday evening that they might attract support from disenfranchised Conservatives to the new centre-ground anti-Brexit grouping in the chamber.
Shortly after the announcement, Mr Corbyn wrote to every party member expressing his disappointment that a “small group” had left and urged the party “must be united”.
But in a longer filmed statement, Mr Watson lamented their departure and in particular the antisemitic abuse suffered by Ms Berger that had preceded her announcement.
He said: “Even a single incident of antisemitism in the Labour Party shames us. Now we have lost Luciana, one of our most dedicated and courageous MPs.
“If someone like Luciana no longer believes there is a home for her in the Labour Party then many other colleagues will be asking themselves how they can stay.
“That’s why time is short for us. To confront the scale of the problem and meet the consequences. To keep others from leaving.”
One source involved in the split on Monday told The Independent that other MPs were close to quitting and would follow depending on what happened over Brexit in the coming weeks.
In his statement, Mr Watson said that “a virulent form of identity politics has seized” control of Labour, and said Mr Corbyn’s team now must “reflect the balance of opinion” across all MPs in the parliamentary party.
He also lashed out the “hard Left”, who he claimed “can be too easily tempted into the language of heresy and treachery”.
It came after the MPs faced a wave of abuse in the wake of their decision to leave, including fellow MP Lloyd Russell-Moyle who compared them to “cowards”.
The Young Labour twitter account posted a line from the party’s anthem, The Red Flag, reading: “Though cowards flinch and traitors sneer, we’ll keep the red flag flying here.”
Shadow chancellor John McDonnell called on the breakaway group to do “the honourable thing” and fight to retain their seats, while Unite union boss Len McCluskey hit out at the “splitters” who had “no stomach for a fight for Labour’s core values”.
The decision to quit the party had been the result of months of soul searching for the MPs, with one telling The Independent: “I’ve been getting out of bed every morning for the past two years thinking, ‘Shall I resign from the Labour Party today or tomorrow?’”
The most recent Brexit votes on 14 February appear to have been a tipping point for some angered by Mr Corbyn’s reluctance to support a second referendum.
One source in the breakaway group said: “We were looking at the amendments that the Labour Party was putting down and hoping, I was hoping anyway, on the 14th we would have had a little more movement on a People’s Vote but in fact we ended up going backwards and it wasn’t referenced at all.
“Clearly a lot of us have had issues with the leadership of the party going back quite some time ... We tried everything to save the Labour Party.”
Mr Corbyn’s response to the poisoning of former Russian spy Sergei Skripal also “crystallised” concerns, another MP said, arguing they were not prepared to sponsor a government led by him.
As she resigned, Ms Berger said Labour had become “institutionally antisemitic”, while Mr Gapes, a former chairman of the Commons Foreign Affairs Committee, told the press conference Labour is now a “racist, antisemitic party”.
He added: “Jeremy Corbyn and those around him are on the wrong side on so many international issues – from Russia, to Syria, to Venezuela. A Corbyn Labour government would threaten our national security and international alliances.”
Mr Umunna called on MPs from Labour and other parties to “leave the old tribal politics behind” and join the new independent group.
He said: “It is time we dumped this country’s old-fashioned politics and created an alternative that does justice to who we are today and gives this country a politics fit for the here and now, the 21st century not the last one.
“We’ve taken the first step in leaving the old tribal politics behind and we invite others who share our political values to do so too.”
As well as other Labour MPs, there has been speculation that some Tories may consider joining the new group, with several facing deselection moves in their local associations due to their soft-Brexit stance.
Among those is the Tory MP for Grantham, Nick Boles, who said: “They’re all good people and I understand completely why they felt driven to leave Labour.
“I have not spoken with any of them about their plans and am totally focused on working with MPs of all parties to stop a no-deal Brexit on 29 March.”
Work now begins in earnest on framing what the Independent Group stands for and how it will be run, with its first meeting due in the coming days.
A source said they needed to get moving quickly or “the machines of the existing parties are going to come after us in a very significant way”.
“It’s D-Day today”, the MP added.
Sources were keen to emphasise their independence from pro-EU campaigns such as People’s Vote and also from prominent figures like ex-Labour prime minister Tony Blair – despite their support for a Final Say referendum.
Scant detail has emerged about how the group is going to be funded, apart from a crowdfunding page which crashed when the announcement was made.
Asked whether they had union funding, one MP said they respected the union movement but joked it was “nice to be free” as most were run by a “tiny clique”.
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