Protests will take place across the country calling for the ban on Palestine Action to be reversed, amid police warnings those showing support for the proscribed group face arrest.
Demonstrations will be held in Manchester, Edinburgh, Bristol, Truro and London on Saturday as part of a campaign coordinated by Defend Our Juries, which has already seen dozens arrested.
The Met said 70 people were arrested at similar demonstrations in Parliament Square over the past two weekends, while Defend Our Juries said a total of 120 had so far been arrested across the UK.
It comes ahead of a High Court hearing on Monday in which the co-founder of Palestine Action, Huda Ammori, will ask for the green light to challenge the Home Secretary’s decision to ban the group under anti-terror laws.
The ban means that membership of, or support for, the direct action group is now a criminal offence punishable by up to 14 years in prison, under the Terrorism Act 2000.
An increased police presence is expected in Westminster as officers police both the Defend Our Juries demo in Parliament Square and a separate large-scale march to Whitehall by the Palestine Coalition.
There will also be a static counter-protest by Stop the Hate at the junction of the Strand and Waterloo Bridge, where the march will pass.
Deputy Assistant Commissioner Ade Adelekan, who is leading the policing operation, also warned his officers will be on alert over the use of chants similar to that of “death to the IDF” led by Bob Vylan at Glastonbury Festival.
He said: “This is also the first large-scale protest on this issue since Glastonbury Festival where offensive chanting led by an artist on one of the stages prompted a police investigation.
“Investigations are also underway, led by Met officers, following similar uses of the same chant in London.”
He went on: “At previous protests, the area between the main march and any counter protest has seen the most heated exchanges. Officers will be particularly alert to conduct, including chanting, in this area and will be working with stewards to ensure crowds keep moving past this point,” he said.
“Where they become aware of behaviour that crosses the line from protest into criminality, they will intervene and take appropriate action.”
Mr Adelekan said those expressing support for Palestine Action “will likely be committing an offence and will very likely be arrested”.
He added: “I would urge those people to consider the seriousness of being arrested under the Terrorism Act and the very real long-term implications – from travel, to employment, to finances – that such an arrest is likely to have for their future.”
He said the best way for protesters to stay within the law is to avoid “threatening, abusive and insulting language” or any support for banned groups.
The Palestine Coalition march will begin at Victoria Embankment and proceed via Westminster Bridge, York Road, Waterloo Bridge, the Strand, and Whitehall, where speeches will be held.
