Extinction Rebellion has launched legal action against the police over a ban on the climate activists' protests in London.
The legal proceedings follow the announcement of a capital-wide ban against the group made under public order legislation yesterday.
Under the current order any assembly of two or more people linked to Extinction Rebellion is unlawful.
Previously, the group were legally able to protest in the pedestrianised area of Trafalgar Square.
In spite of the ban, activists continued protesting in the capital on Tuesday. More than 1,400 people have been arrested since the protests began last Monday.
The move comes amid growing criticism of the ban, made under public order legislation already used to restrict the action to Trafalgar Square.
Activists continued protests in the capital in defiance of the police order, targeting the Department for Transport and locking themselves to a caravan on Millbank.
Human rights lawyer Tobias Garnett, working for Extinction Rebellion, said the group would be filing a High Court claim challenging the ban on the grounds it is "disproportionate and unlawful".
The group were planning to file a claim on Tuesday afternoon, and was seeking an expedited hearing.
However, they decided to give the police until 4pm to respond.
Speaking at 4.30pm Mr Garnett said: "We have put a letter into the police basically asking them to withdraw the Section 12 order.
"We have given them a deadline until 4pm.
"It is now 4.30pm, we have not heard from them.
"We plan, if we have not heard from them by tomorrow morning, we will go to the high court.
"We will make an argument that the prohibition on protest is disproportionate and unlawful.
"We will argue that it is an infringement on articles 10 and 11 of the Human Rights convention, and it criminalises anyone who wants to protest."
He added that the police order "risks criminalising anyone who wants to protest in any way about the climate and ecological emergency that we face".
Under the current order, any assembly, classed as a gathering of two or more people, linked to Extinction Rebellion in London is unlawful.
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Lawyers have questioned the legality of ban, aimed at halting further protests after more than a week of disruption by the environmental activists in London, while a number of politicians expressed outrage over the move.
Anti-Brexit barrister Jo Maugham QC claimed the move was a "huge overreach" of police powers, human rights lawyer Adam Wagner called it "draconian and extremely heavy-handed", and Allan Hogarth from Amnesty International said it was "unacceptable".
Shadow home secretary Diane Abbott said: "This ban is completely contrary to Britain's long-held traditions of policing by consent, freedom of speech, and the right to protest."
Green Party MEP Ellie Chowns, who was arrested in Trafalgar Square, Green MP Caroline Lucas and shadow policing and crime minister Louise Haigh also spoke out against the move.
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