As Labour Party leader Jeremy Corbyn fights off attempts by his own MPs to dethrone him, thousands of his grassroots supporters across Britain are rallying in his defense.

Corbyn supporters were left outraged when, less than 24 hours after the Brexit referendum results, members of Labour’s parliamentary group (PLP) called for the leader to resign, accusing him of leading a halfhearted campaign to remain.

The London demonstration, organized by the grassroots Labour network Momentum, quickly went viral, with over 3,500 people vowing to attend on social media.

A 38 Degrees petition-turned-Vote of Confidence in the Labour leader collected a prompt 202,000 signatures in the space of a day.

Momentum organizer Marsha-Jane Thompson told RT: “It’s amazing to see how many people responded already.

“We’ve got 200,000 people who’ve signed a petition saying they have got confidence in Jeremy.

I’d find it virtually impossible to endorse a new leader born from a #LabourCoup My believe in democracy is stronger than party politics. — Harry Leslie Smith (@Harryslaststand) June 27, 2016

Corbyn himself addressed the roaring crowd, speaking in favor of more unity while blaming the media for trying to weaken the party by forcing a wedge between him and its supporters.

“Don’t let the media divide us. Don’t let the people who wish us ill divide us. Stay together, strong and united for the kind of world we want to live in,” he said, stressing that a “blame culture” is counter-productive. Instead, Corbyn called on his supporters to focus on reaching “the social justice to which we all aspire.”

The so-called Labour coup, she added, showed “how disrespectful the members of the PLP are being towards the grassroots, refusing to accept Jeremy’s mandate.”

In case of a new leadership contest, Thomson went on: “Jeremy is going to be on the ballot paper and Jeremy is going to win.

“Apart from being very disrespectful it’s just a complete waste of time and money.”

Corbyn was elected Labour leader in September 2015 with a majority of almost 60 percent.

The general secretaries of the firefighters union (FBU) and the communications unions (CWU), Matt Wrack and Dave Ward, are set to deliver speeches in defense of Corbyn in Westminster.

Wrack, a Corbyn supporter from the very beginning of the Islington MP’s campaign, said ahead of the demonstration: “If there was any right time to back the Labour Party leader, it is now. But it’s not just the right time – it is critical.”

Unwavering support for the Labour leader came also from one of Britain’s biggest trade unions, Unison, whose general secretary Dave Prentis urged his members to unite in times of “huge threats to our economy.”

People’s Assembly Against Austerity secretary Sam Fairbairn, meanwhile, said: “The reason why the right wing in the Labour Party are so opposed to Jeremy is not because they think he’s unelectable, it’s because they know that the anti-austerity politics that Jeremy represents has a real chance of winning.

“The movement on the streets, workplaces and our communities won’t rest until austerity is history and will back Jeremy all the way.”