The Metropolitan Police has warned those attending Saturday's protest by far-right groups and rival anti-fascists to demonstrate peacefully or face arrest.
Protesters from the anti-Islam English Defence League (EDL) and Britain First groups will demonstrate near Westminster Bridge on Saturday, April 1, where they will be met by counter-demonstrators from the London Anti-Fascist Network.
The far-right groups announced their plans to protest at the site in the wake of the March 22 terror attack, in which Muslim convert Khalid Masood killed three pedestrians with his vehicle on Westminster Bridge and fatally stabbed a police officer before being shot dead.
With previous demonstrations by the groups having resulted in violent clashes, the Met has issued a series of restrictions on where demonstrators can gather, and warned those planning to attend that they face arrest if they disobey them.
Chief Superintendent Catherine Roper said: "If you want to protest on Saturday 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."
"The decision to apply Section 12 and 14 of the Public Order Act was taken based on current tensions and concerns, the current intelligence picture about Saturday and previous marches and protests held by similar groups."
The EDL must conduct its protest along a route from Trafalgar Square to Victoria Embankment near Westminster Bridge, where three pedestrians were killed in the attack, with Britain First demonstrators restricted to a route between Charing Cross railway station to Victoria Embankment.
Anti-fascists had planned to meet the EDL at Trafalgar Square at midday, but are now restricted to gathering at Victoria Embankment.
In 2013, there were 160 arrests when EDL supporters clashed with counter-demonstrators at a protest in Tower Hamlets, east London, home to one of London's largest Muslim communities.
Experts have warned that far-right groups may attempt to capitalise on the Westminster attack to recruit supporters, with former EDL leader Tommy Robinson appearing at the scene of the Westminster attack and criticising Islam only hours after it happened.