Thousands took to the streets of London to protest against military intervention in Syria for the second time in four days.
Chants of “David Cameron shame on you!” and “Don’t bomb Syria!” rang out across Parliament Square.
Lindsey German, the convenor of Stop the War, told the crowd: “We are here to say one very simple thing: don’t bomb Syria.
“Do not this time go and bomb a country where you make it even worse than it was before.”
Salma Yaqoob, the head of the Birmingham Stop the War coalition, said “we don’t seem to have learned a single thing” from the invasion of Iraq.
“When we bomb other people’s countries, we do not become more safe. We become less safe.
“If you bomb them we will not be safe at home.”
The emergency protest was called by the Stop the War coalition ahead of Wednesday’s vote on airstrikes.
The coalition had condemned as “deplorable” Jeremy Corbyn’s decision to grant a free vote to Labour MPs, with Andrew Murray, the group’s chairman, saying it had “cleared the way” for the Commons vote on air strikes.
More than 3,500 people said they were going to the event on Facebook, where organisers wrote: “We must do everything we can to stop MPs voting the UK into its fourth war on a Muslim country in 14 years.”
A statement on the Stop the War website read: “Britain has been the most aggressive country in Europe over the last 15 years, leading military interventions in Afghanistan, Iraq and Libya.
“Yet it has done little to help the victims of the wars it so enthusiastically pursues and it has been at the forefront of opposing a humane policy towards refugees.
“Another destructive bombing campaign is no solution whatsoever. It will make moves toward a political solution harder. It risks intensifying and widening what is already a catastrophic war.”
Tuesday’s protest comes after thousands of people protested outside Downing Street on Saturday.
Parts of Whitehall were brought to a halt during the event, which included speakers such as the actor Mark Rylance and the musician Brian Eno.
A statement issued by more than 50 student leaders was issued earlier on Tuesday.
It read: “British military action will not defeat Isis and risks increasing the terrorist threat both to the peoples of the Middle East and to Britain.”