Police have issued a warning of mass arrests to protestors planning to come out in support of Palestine Action this weekend.
Campaigners will attend demonstrations across the country on Saturday in support of the proscribed group.
The plan was outlined at an event hosted by Cage International in Birmingham, where former Guantanamo Bay detainee Moazzam Begg called on people to join the demonstration in support of Palestine Action.
Hundreds are expected to attend a protest in London this Saturday, in a move by pressure group Defend Our Juries to highlight both the ongoing humanitarian crisis in Gaza and their right to protest.
In response to reports of mass protests, the Metropolitan Police said "anyone showing support for the group can expect to be arrested."
"We are aware that the organisers of Saturday's planned protest are encouraging hundreds of people to turn out with the intention of placing a strain on the police and the wider criminal justice system," said a spokesperson.
Defend Our Juries said: "If we are allowed to protest peacefully and freely, then that is no bother to anyone.”
Palestine Action was proscribed as a terrorist group on July 5, which made it illegal to express support for the group.
Since then, more than 100 people have been arrested for allegedly taking part in demonstrations in support of Palestine Action.
The co-founder of Palestine Action won the right to raise a legal challenge against the proscription and a judicial review of the legality of the group is due to be heard in the Autumn.