In the biggest party schism since the 1980s, seven MPs quit yesterday in protest at Mr Corbyn’s leadership, accusing him of allowing Labour to become “institutionally antisemitic” and claiming a Corbyn government would “threaten our national security”.

The Labour deputy leader and the party’s most senior Scottish MP led warnings that more walkouts would follow unless Mr Corbyn did more to embrace his critics and tackle a culture of harassment and bullying. MPs Luciana Berger, Chris Leslie, Gavin Shuker, Mike Gapes, Angela Smith, Ann Coffey and Chuka Umunna wrote to party officials informing them of their resignation moments before holding a press conference to reveal their plans.

They appealed to others angry at the deadlock over Brexit and the looming risk of a no-deal exit from the EU to quit their parties and join a new “Independent Group” in the centre ground.

MPs (left to right) Chris Leslie (Ann Coffey, Angela Smith, (both hidden left), Gavin Shuker, Luciana Berger, Chuka Umunna and Mike Gapes, after they announced their resignations from Labour

Mr Corbyn said he was “disappointed” by the announcement. Shadow chancellor John McDonnell challenged the seven to resign from Parliament and fight by-elections under their new independent banner.

But in a stark message from Mr Corbyn’s deputy, Tom Watson said he “feared this day would come” and warned that “unless we change, we may see more days like this”.

Mr Watson criticised the handling of antisemitism allegations and said Ms Berger had fallen victim to “a virulent form of identity politics that has seized the Labour Party”.

He called for an immediate reshuffle of the frontbench team to reflect differing opinions in the parliamentary Labour Party.

Struggling to contain their emotion, the seven MPs condemned the direction of their former party since Mr Corbyn took office. Ms Berger, who has faced death threats over her criticism of the Labour leadership, said she had become “embarrassed and ashamed” of representing a party she claimed was “institutionally antisemitic”.

Mr Leslie said Labour had been “hijacked by the machine politics of the hard left” and claimed Mr Corbyn’s hostility to business and Nato flowed from a “narrow, outdated ideology”.

Mr Umunna encouraged members of all parties angry at the conduct of politics to support their group. Established parties “can’t provide the change because they have become the problem”, Mr Umunna said. He added: “If you are sick and tired of politics as usual, guess what? So are we.

“If you want an alternative, please help us build it. The bottom line is this – politics is broken. It doesn’t have to be this way. Let’s change it.”

Responding to the resignations, Mr Corbyn said: “I am disappointed that these MPs have felt unable to continue to work together for the Labour policies that inspired millions at the last election and saw us increase our vote by the largest share since 1945.”

There were contrasting responses from Labour’s union backers. Unison general secretary Dave Prentis said the party had to “look long and hard at the reasons why the MPs feel they are no longer able to stay”.

But Unite general secretary Len McCluskey – one of the key powers behind Mr Corbyn’s leadership – accused the breakaway MPs of “hypocrisy” for standing for election on a Labour manifesto.

“All of them got massive increases in their majorities,” he said. “It wasn’t because of their own personal charisma. It was because of the manifesto, which promised to respect the 2016 referendum.”

Liberal Democrat leader Sir Vince Cable said he was “open to working with like-minded groups and individuals” to bring about a second EU referendum and would seek talks with the members of the Independent Group.

The SNP’s Westminster leader Ian Blackford said the split in Labour showed Westminster was “now completely dysfunctional”.

He said: “Labour are not fit for purpose – they are failing as an opposition, failing over Brexit and failing their own MPs.”

Sick of Jeremy Corbyn and sick of ‘politics as usual’, Labour MPs walk out