Musicians, MPs, activists and comedians have pledged to stage the biggest demonstration in British history in protest against Donald Trump’s visit to the UK.

A letter sent to the Guardian by the newly formed Stop Trump Coalition, and signed by 90 figures from across arts and politics, damningly referred to the US president’s actions as “dangerous and divisive” and said he “directly threatens steps towards tackling climate change, fighting discrimination, inequality, peace and disarmament”.

Signatories include singers Lily Allen and Paloma Faith, comedian Frankie Boyl, Bianca Jagger, former Labour leader Ed Miliband, Tim Farron, the Liberal Democrat leader, journalist Owen Jones, Green party co-leader Caroline Lucas, Leanne Wood, the Plaid Cymru leader, and Labour MP Clive Lewis.

They hope their combined backgrounds and spheres of influence will help mobilise 1 million people on to London’s streets to make their opposition to Trump heard.

The letter also targeted Theresa May and her government, who they accused of normalising Trump’s agenda, which has included stopping all refugees from entering the US as well as anyone who holds a passport from seven Muslim-majority countries.

“Those who are often already marginalised and discriminated against – especially Muslims and migrants – have been particular targets for Trump,” the letter said.

“People in Britain never voted for this. It is our duty as citizens to speak out. We oppose this state visit to the UK and commit ourselves to one of the biggest demonstrations in British history, to make very clear to our government, and to the world, this is not in our name.”

The date of the protest has not been decided, though the organisers hope to build on the momentum that saw 30,000 people gather outside Downing Street on Monday night, along with thousands of similar demonstrations across the UK, to protest Trump’s immigration policies and May’s refusal to openly condemn his travel ban.

Lewis said: “Challenging Trump and the ideas that support him has never been so critical. As such protests are a small but important part in making the political space for our progressive ideas to be heard.”

The Stop Trump Coalition will stage an initial day of protest on 20 February, the same day the petition to prevent Trump being given an official state visit to the UK will be debated in parliament. It currently has more than 1.8m signatures.

• This article was amended on 2 February 2017 after the list of signatories to the letter itself was amended to remove a name that had been included in error.