Thousands of anti-fascists are expected to attend a central London protest on Sunday to counter a march by the far-right campaigner known as Tommy Robinson and his supporters.

The counter-protest has been organised by the Labour-supporting Momentum group and partners. It forms part of a drive to increase the party’s involvement in peaceful anti-fascist activity fuelled by fears about the threat posed by Robinson and political groups such as Ukip.

A new group within the party, Labour Against Racism and Fascism, has been created and Momentum has been trying to counter a far-right social media effort which some members believed was often more sophisticated than its own web presence. A new Momentum video taking aim at Robinson, whose real name is Stephen Yaxley-Lennon, this week had 1.5m views in less than 28 hours.

"Did you find any hatespeech"? 🤔🤔🤔



Take a stand against the new far right this Sunday: https://t.co/w8WGv7d88T pic.twitter.com/pOXEJrjSvr — Momentum (@PeoplesMomentum) December 3, 2018

The shadow chancellor, John McDonnell, has called for Labour members to join the counter-protest, which is also backed by London Young Labour and the Stop Trump Coalition.

He said: “A newly energised, well-funded network of hate is emerging, from Steve Bannon in the US to the former EDL [English Defence League] leader Tommy Robinson at home, and it threatens the very fabric of our nation. The Labour movement must be front and centre in opposing them.”

Thousands were expected to attend the Robinson event, which involves a march on Whitehall three days before MPs vote on Theresa May’s Brexit package and has been billed as a “Brexit betrayal rally”.

Laura Parker, Momentum’s national coordinator, said: “There has been a reluctance at times from some in the mainstream of Labour to engage in events like this in the past. It’s not a criticism of those who still care deeply about it, but this is an area where Labour has sometimes been lacking while other organisations have dominated.

“I think that the threat from the far right is now obviously so huge, however, that there has to be a peaceful mobilisation by pretty much everybody, from trade unions to party members and others.”

The march follows Momentum’s recent mobilisation in support of counter-marches against events by groups such as the Democratic Football Lads Alliance (DFLA).

Niroshan Sirisena, a Labour councillor in Croydon and a Momentum organiser, said he and others set up Labour Against Racism and Fascism weeks ago as part of an attempt to develop the party’s anti-racism policies at a constituency level.

“Labour is an anti-racist party, but I think it has to do a little more than say that it is one,” said Sirisena, who has also been involved in distributing anti-racism leaflets at Premiership matches as part of a move to counter the far-right focus on football fans. The initiative started at a recent Crystal Palace match against Tottenham, whose fans include DFLA activists.

“We want to continue getting our message out there,” he said, “whether it is at a national level or local level, because we have definitely seen a threat. Around Croydon in recent times, for example, we’ve had to organise to clean up graffiti that appeared around the area in support of Tommy Robinson when he was last in prison.”

Sirisena spoke of a post-referendum “malaise” of racism that was often not necessarily associated with the far right but included physical attacks on migrants and people of colour.

The Metropolitan police have imposed strict conditions on the times and locations those taking part could protest, and warned that anyone who commited acts of violence would be arrested.

The deputy assistant commissioner, Laurence Taylor, the Met’s gold commander for the operation, said: “If you want to protest on Sunday we ask that you do so peacefully, no matter what your view. We will adopt a robust arrest policy on anyone who attends and is intent on violence and disorder, or is in breach of these conditions.

“Experience has shown us that when groups with conflicting views come together it can create tension and disorder, not just on the day itself but in the longer term. We have had to carefully consider how to balance the right to protest with the potential impact on our communities and our ability to manage any disorder that may have resulted from these protests going ahead as they were suggested.”