Hundreds of pro-Palestinian protesters gathered outside Sir Keir Starmer's office in Camden, north London, as part of 100 events taking place across the UK, calling for an immediate ceasefire.
Crowds could be heard chanting “from the river to the sea, Palestine will be free” and “Keir Starmer's a wasteman” as they blocked the road in Camden leading to his constituency office.
It comes after 56 Labor MPs defied their leader's position to back a ceasefire in the fighting to support the ceasefire in a Commons vote.
The march to Sir Keir's office was part of a national day of action on Saturday, with more than 100 rallies taking place across the UK instead of a major march in central London.
In Glasgow, politicians from the SNP, Scottish Labor and the Scottish Greens addressed a crowd of 18,000, with many in attendance writing their names on their hands as a symbol of solidarity with the citizens of Gaza.
Thousands also took to the streets of Dublin in solidarity with the Palestinian people, with the protest starting at the Garden of Remembrance and crossing the River Liffey before a sit-in at the Foreign Office building, Iveagh House.
Meanwhile, protesters staged sit-ins at major UK train stations, prompting increased policing on rail networks, with five arrested in Waterloo, London.
British Transport Police (BTP) deployed increased officer patrols in England, Scotland and Wales on Saturday, but videos shared on social media showed a small crowd sitting on the floor at Victoria Victoria station, while the force confirmed another group of around 25 people had done the same at Leeds station shortly after 2pm.
Around 200 protesters gathered on London Bridge and were dispersed by police, while around 100 were evacuated from Waterloo, with train services at neither station affected.
A group of protesters who were turned away from the station then made their way to Westminster Bridge, where they sat in the street before moving towards Parliament Square, the Metropolitan Police said.
The force told X, formerly Twitter: “We believe the group in Parliament Square is a combination of pro-Palestinian protesters and Just Stop Oil activists.
“We have arrested a prominent Just Stop Oil activist from within the group. We have a significant number of officers ready to respond if there is further disruption on the road.”
During the afternoon, 10 rallies were held across the capital, including Islington, Redbridge and Tower Hamlets. As a result, the Metropolitan Police said a “significant” police operation was planned for the capital this weekend.
They said they would target deployments in areas “with significant Jewish or Muslim communities”, which they said “continue to experience heightened uncertainty and fear in light of events in the Middle East and their impact here in London”.
Previous weekends have seen thousands of protesters and counter-protesters converge on the capital.
A spokeswoman for organizers Stop The War Coalition said Saturday's day of action comes ahead of a national demonstration planned for next Saturday.
Ben Jamal, director of the Palestine Solidarity Campaign, said the rallies were organized to show that “ordinary people” support the ceasefire.
On Wednesday afternoon, MPs voted by 293 to 125, a majority of 168, to reject the SNP's King amendment calling for “all parties to agree to an immediate ceasefire”.
In a statement after the vote, Sir Keir said he regretted that party colleagues did not support his position before saying he was more focused on the plight of people in Gaza than managing divisions within Labour.
Mr Starmer called for humanitarian pauses. He has argued that a ceasefire would allow Hamas to regroup and launch further terror attacks on Israel.
Jess Phillips, the shadow minister for domestic violence and protection, was among 10 vanguards who rebelled against his order.