Organisers behind an emergency rally to drum-up support for Jeremy Corbyn have been forced to cancel the event due to "overwhelming" demand. A spokeswoman for Momentum, the left-wing pressure group, told IBTimes UK that the original venue of Congress House, London, was too small to fit the activists.

"It was already 50% overcapacity within a couple of hours [of advertising the event] and we were a bit concerned of so many people being down there," the spokeswoman explained. The group is now looking to reschedule the rally at a larger venue and hold the event "potentially tomorrow [30 June], but possibly early next week".

Corbyn was scheduled to speak at the rally alongside shadow chancellor John McDonnell and new shadow health secretary Diane Abbott.

More than a thousand protesters gathered in Parliament Square on Monday night to show their support for the left-winger as he faces a leadership coup.

Since then Labour MPs have overwhelmingly backed a motion of "no confidence" against Corbyn in reaction to his decision to sack Hilary Benn as shadow foreign secretary and Labour heartlands across England and Wales backing a Brexit, the opposite position to that Corbyn campaigned on.

David Cameron, who resigned after the Leave result, has also urged Corbyn to quit as has former Labour leader Ed Miliband, among other well-known figures in the party.

In a related video, crowds rally for Jeremy Corbyn in Parliament Square IBTimes UK

But Corbyn, who attracted almost 60% of the vote in Labour's 2015 leadership election, has taken a defiant stance and vowed to stay on. "Labour has the responsibility to give a lead where the government will not. We need to bring people together, hold the government to account, oppose austerity and set out a path to exit that will protect jobs and incomes," he said in a statement.

"To do that we need to stand together. Since I was elected leader of our party nine months ago, we have repeatedly defeated the government over its attacks on living standards."

He added: "Last month, Labour become the largest party in the local elections. In Thursday's referendum, a narrow majority voted to leave, but two thirds of Labour supporters backed our call for a Remain vote.

"I was democratically elected leader of our party for a new kind of politics by 60% of Labour members and supporters, and I will not betray them by resigning. Today's vote by MPs has no constitutional legitimacy.

"We are a democratic party, with a clear constitution. Our people need Labour party members, trade unionists and MPs to unite behind my leadership at a critical time for our country."

The former shadow business secretary Angela Eagle, who took a prominent role in the party's pro-EU campaign, is expected to run against Corbyn in a forthcoming leadership election. But the influential trade unions, including Unite and Unison, have also maintained their support for Corbyn.