A total of 175 people have been arrested in central London during protests in support of the proscribed group Palestine Action the Metropolitan Police has said.

Organisers Defend Our Juries said hundreds took part in demonstrations backing Palestine Action – a group which was proscribed by the government in July making it illegal to show any support or affiliation to them.

Demonstrations went ahead despite calls from ministers and police who called for protests to be postponed following Thursday’s deadly synagogue attack in Manchester.

Sir Keir Starmer had urged protesters to “respect the grief of British Jews”, while Jewish figures also criticised the protests.

Defend Our Juries member, Sir Jonathon Porritt, said had “no doubt” that “everyone taking part in the silent vigil today will demonstrate huge respect and real grief for those affected by the absolute atrocity at Heaton Park”.

The former advisor to the King when he was the Prince of Wales told Radio 4’s Today programme: “I do not think that means that we should be asked to give up on our right to stand up for those who are being devastated by an ongoing, real-time genocide in Gaza.”

Those taking part “would have the deepest concern about growing levels of antisemitism”, he added.

Ahead of the demonstrations, the Met Police said it would deploy 1,500 officers to Trafalgar Square to deal with the protesters.

In an update on Saturday afternoon, the Met said the bulk of those arrested were detained for gathering in Trafalgar Square; while six were arrested for unfurling a banner backing the proscribed group on Westminster Bridge earlier in the day.

The force said each arrest took time because “many of those arrested won’t walk out of the square and need to be carried”.

The Met said this is a process which requires a minimum of five officers to do so safely.

On Friday, the Met wrote to Defend Our Juries to raise concerns about the amount of police resources the protest would divert at a time when “visible reassurance and protective security” was needed for communities.

But the group, which has led demonstrations against the ban on Palestine Action, defied these calls and went ahead with the protest.

Minutes before the main event started in Trafalgar Square, Defend Our Juries managed to hold two banners over the north side of Westminster Bridge which read: “I oppose genocide” and “I support Palestine Action”.

The Met said officers removed the banners minutes later, and arrested those involved for supporting a proscribed organisation.

A similar event held by Greater Manchester Friends of Palestine also took place where a crowd of around 100 pro-Palestinian supporters gathered outside Manchester Cathedral ahead of a march.

The protests were held just days after two Jewish men – Adrian Daulby and Melvin Cravitz – were killed after Jihad Al-Shamie drove a car into people outside Heaton Park Hebrew Congregation synagogue in Manchester.

The knifeman then tried to force his way into the synagogue before being shot dead by armed police. Three others were injured in the attack.

Ahead of the demonstrations, the Community Security Trust (CST) charity – which provides security for the Jewish community – told BBC Radio 4’s Today programme, the protests were “phenomenally tone deaf”.

Dave Rich said: “For so many people who claim to care about human rights and care about freedoms, to be taking police resources away from protecting the rights and freedoms of Jewish people to live their lives and go to synagogue in safety, all to support a proscribed terrorist organisation, which is not the same thing as supporting the Palestinians.

“The two are not the same. And I think it’s remarkably self absorbed and insensitive to say the least.”

The group has urged the Met to “prioritise protecting the community, rather than arresting those peacefully holding signs” in support of Palestine Action.

The government proscribed Palestine Action under anti-terrorism legislation in July, after activists broke into an RAF base and damaged two military aircraft earlier in the year.

At various protests since then, hundreds have been arrested for showing support for the group, which has won permission to challenge the ban.