London (AFP) - Britain's opposition leader Jeremy Corbyn condemned "internal manoeuvring" after more than half his top team resigned in barely 24 hours, but insisted he would not go himself despite a rising tide of criticism of his role in the Brexit crisis.

Twenty members of the Labour leader's shadow cabinet have so far resigned in a rolling series of departures triggered by Corbyn's weekend sacking of his foreign affairs spokesman Hilary Benn.

The veteran socialist, widely blamed for failing to rally the party's core working-class vote base to support the "Remain" campaign, said the country was divided after last Thursday's shock vote.

"Our country is divided and the country will thank neither the benches in front of me, nor those behind, for indulging in internal... manoeuvring at this time," he told the House of Commons in a debate with Prime Minister David Cameron.

He insisted he would stand again as leader if another contest was called.

Corbyn was flanked by his stony-faced deputy Tom Watson in the front row of green Labour benches, his own MPs facing the Conservatives ranked behind Cameron across the parliamentary chamber.

Corbyn had earlier insisted would not betray the trust of the party members who elected him only last September, and vowed to "reshape" his shadow cabinet.

"Don't let the media divide us, don't let those people who wish us ill divide us, stay together, strong and united for the kind of world we want to live in," he told a cheering rally of supporters outside parliament.

The gathering of about 2,000 of the young grassroots activists brandished placards with slogans such as "Corbyn In, Tories Out".

But Daily Mirror, a historically Labour-supporting newspaper, was not on side, instead adding its voice to calls for Corbyn to leave: "Go now" read its front page.

- No-confidence motion -

The drama within the opposition Labour party broke over the weekend with the sacking of foreign affairs spokesman Hilary Benn, who had told Corbyn he did not have confidence in his leadership.

"He's a good and decent man but he is not a leader, and that's the problem," Benn told the BBC.

Benn's departure triggered a wave of resignations, hour by hour, with many of his team publishing letters of criticism on Twitter.

"As much as I respect you as a man of principle, I do not believe you have the capacity to shape the answers our country is demanding," wrote shadow health secretary Heidi Alexander.

"It's just not working," a tearful shadow business secretary Angela Eagle told the BBC.

The result of a secret ballot of Labour MPs on a no-confidence motion on Corbyn is expected to be announced on Tuesday.

Any challenger to Corbyn would need the support of 20 percent of the party's 229 MPs and it would then be put to party members, who are strongly supportive of the leader.

Critics say Corbyn -- who for decades had expressed eurosceptic views -- could have done more to sway voters ahead of last Thursday's referendum.

Polling showed one third of Labour voters chose to leave the European Union in Thursday's historic vote, against the advice of the majority of the party's MPs and the leadership.

Deputy Labour leader Watson issued a statement saying he was "saddened" that so many colleagues had decided to quit.

"My single focus is to hold the Labour Party together in very turbulent times. The nation needs an effective opposition, particularly as the current leadership of the country is so lamentable," said Watson.