The singer Charlotte Church and veteran peace campaigners are among hundreds who have signed a letter describing the move to ban the group Palestine Action as “a major assault on our freedoms”.

Trade unionists, activists and politicians have also added their names to the letter opposing the group’s proscription under anti-terrorism laws last week.

Church said: “I sign this letter because history shows us that when people stand up to injustice, those in power often reach for the same old playbook: label dissent as dangerous, criminalise protest, and try to silence movements for change by branding them as extremists or terrorists.

“From the suffragettes to the civil rights movement, what was once condemned as radical disruption is now celebrated as moral courage. We must remember this pattern – and refuse to let our rights be eroded by fear. This is not new, and we will not be silenced.”

“By signing this letter I am not inviting support for any proscribed organisation – people can make their own minds up – but I am making a clear and strong stand against the abuse and misuse of terrorism laws to malign direct action protest.”

A ban on Palestine Action, which uses direct action to mainly target Israeli weapons factories in the UK and their supply chain, was voted through by parliament this month. Being a member of, or showing support for the group is now a criminal offence after a last-minute legal challenge to suspend the group’s proscription failed.

The open letter states: “Peaceful protest tactics which damage property or disrupt ‘business-as-usual’ in order to call attention to the crimes of the powerful have a long and proud history. They are more urgent than ever in response to Israel’s genocide against the Palestinian people.”

Other signatories to the letter include the environmental and human rights campaigner Angie Zelter, who was acquitted after disarming a BAE Hawk Jet and who also destroyed infrastructure supporting Britain’s Trident nuclear weapons system.

She said: “Effective protest often disrupts ‘business as usual’. Halting the cruel arms trade and the dangerous militarisation of our society is really important to me. I have been involved in peaceful civil resistance for decades. I am in full support of civil resistance and of people involved in upholding international law.”

Elected representatives who have signed the letter include James Dornan, the Scottish National party MSP for Cathcart who last week put a motion to the Scottish parliament calling for the proscription of the Israel Defense Forces as a terrorist organisation.

It was also signed by Gerry Carroll, the socialist activist and member of the legislative assembly for West Belfast, along with Plaid Cymru, Labour and Co-operative councillors.

A spokesperson for Glasgow Trades Union Council, which is collectively backing the letter, said: “As the UK government is attacking our civil liberties, we must ask ourselves if not now, then when?”

One of the organisers of the letter was Anne Alexander, a researcher and UCU activist at the University of Cambridge, who said more than 900 people had signed. She said: “The response to this open letter shows that people up and down the country want to stop arms going to Israel and that they don’t agree that a direct action group are ‘terrorists’ because they tried to disrupt the supply chain fuelling a genocide.”

Other signatories include Leanne Wood, the former leader of Plaid Cymru, and Suresh Grover, the veteran civil rights and anti-racist campaigner who was a founder of the Southall Monitoring Group and led campaigns to help the families of Stephen Lawrence, Zahid Mubarek and Victoria Climbié.

The draft order to amend the Terrorism Act 2000 and proscribe the group, laid by the home secretary, Yvette Cooper, passed the Commons on 2 July by 385 votes to 26.

The order also bans two neo-Nazi groups, the Maniacs Murder Cult and the Russia Imperial Movement. Some MPs and human rights organisations critical of the government’s position suggested that bundling Palestine Action with the white supremacist groups had put political pressure on MPs to back the measure.