Met police preparing for large scale far-right and pro-Palestine protests in London | Tommy Robinson

British police are preparing to mount one of their largest scale operations in recent memory with more than 100,000 protesters set to march through the streets of London on the same day as the FA Cup final in Wembley.

The Guardian understands that officers in vast swathes of central London will be granted extra powers in order to police the far-right Unite the Kingdom march organised by Stephen Yaxley Lennon, better known as Tommy Robinson.

At the same time, as smaller counter march organised by pro-Palestine protesters will take place, with the two events to be separated by police.

The scale of the last UTK march in September stunned both organisers and police with more than 150,000 joining a crowd that occupied Parliament Square in Westminster.

The prime minister, Keir Starmer, has said the rise of the far right represented “a fight for the soul of this country”, and the march comes after Nigel Farage’s Reform UK won the biggest share of the vote at last week’s English council elections.

Britain’s largest Muslim group has warned people to avoid central London this weekend amid fears the second event could reach a similar size.

The Metropolitan police has 4,000 officers on duty, backed up by armoured Sandcat vehicles and drones. Most will be deployed to police the UTK march, and keeping away counter protesters.

The situation is complicated by the cup final between Manchester City and Chelsea, which kicks off at 3pm. The Met this week said football hooligans have in the past supported Robinson, and social media videos features calls for them to join Saturday’s protest.

The Unite the Kingdom march last year, which was backed by money from the US, featured stages where hate speech amplified over Westminster by a string of extremist participants who denounced Islam and promoted Christian nationalism. Saturday’s event will see the far right thronging streets that house Britain’s most powerful institutions in Whitehall.

The Guardian understands police will try to seek prosecutions not just against speakers at both marches, but organisers for conspiracy, if comments from the stage are judged to be inciting hatred.

The pro-Palestinian rally numbers will be boosted by anti-racists countering the much larger far-right protest, with numbers expected to be between 15,000 and 40,000.

Police believe prosecutors are now more likely to agree charges for what they consider to be antisemitic chants or slogans, with “globalise the intifada” leading to charges against three people. Previously prosecutors had declined to prosecute for the slogan.

Planned to speak at the far-right rally, according to its advertising, is the mother of a woman killed by an asylum seeker, and the American conspiracy theorist Glenn Beck, a former anchor on rightwing US channel Fox News, who left amid claims he was too extreme for the Rupert Murdoch-owned network.

Robinson went to the US in February where in Washington more than a dozen law makers met him, and he was also hosted by the US state department. Previously he had been banned from entering the US because of criminal convictions.

The promotion material features an AI-generated video that denounces Muslims and ends with a sequence where Lennon is the hero on stage adored by a crowd of tens of thousands and contains the line: “Tommy Robinson’s vision, this is our destiny.”

While the video for UTK may be AI fantasy, Nick Lowles of Hope Not Hate warned the reality is that Robinson is popular among a significant minority of Britons.

Polling shows Lennon is known by more than 80% of respondents, and while the number of those disliking him is high, 17% like him: “Lennon can put more people on the streets than any other person. He is a phenomenon,”, said Lowles.

In a video on Friday, Robinson appealed to officers policing the march not to rush to draw their batons: “We’re not coming for a big battle … the people that are there tomorrow, are the people at the school gates with you.”

In another video he urged supporters to stay calm if provoked and to “win by smiling at them”, adding: “This is not an event to bring your anger.”

The Muslim Council of Britain warned the march puts Muslims “at risk of being subjected to increased violence and hatred”. It said the last event “featured speakers who openly incited hatred, chanted anti-Muslim slogans and unashamedly encouraged violence and civil disobedience on Britain’s streets”.

Dr Wajid Akhter, secretary general of the Muslim Council of Britain said: “Nobody should be forced to walk Britain’s streets in fear of their safety. But when irresponsible political rhetoric, toxic social media algorithms and double standards in policing continue to act as enabling factors for open racism, and violence is promoted on Britain’s streets, the downward spiral will accelerate.”