An order attempting to ban Extinction rebellion protests in London was unlawful, the high court has heard, as lawyers for the group challenged what they described as an abuse of power by police.

Seven prominent supporters of XR brought judicial review proceedings against the Metropolitan police after the force last Monday issued the order under section 14 of the Public Order Act to demand that that the group’s activists “cease their protest(s) within London”.

It was considered an attempt to curtail the group’s two-week “autumn uprising” – a series of non-violent direct action protests in the capital – and was criticised by the civil rights groups Amnesty International UK, Article 19 and Liberty as an assault on the right to protest.

If the judicial review is successful, lawyers for XR suggest that hundreds of protesters arrested under the order may have a case against the Met that their detention was unlawful.

Making the case for XR on Thursday, Phillippa Kaufmann QC told Mr Justice Dingemans and Mr Justice Chamberlain they should quash the Met’s use of section 14 on the basis that it went beyond the law and was framed so unclearly that it was an abuse of power.

Section 14, the court heard, should only be applied to a single continuing assembly. But the Met had used the power to attempt to ban the whole of XR’s uprising, which Kaufmann said comprised a number of assemblies, both continuing and intended.

She further argued the existing assemblies banned under the order were not clearly identified by police, which as a result “created a situation where individuals were uncertain whether the restrictions applied to them or not”.

In response, Ian Skelt, for the Met, argued that the protest had been publicised as a single event with the aim of “intentional civil disobedience”, which had caused widespread disruption to the community.

Given the London-wide nature of the protest, the court heard, long lists of roads or postcodes or other descriptions would have been even less certain than the conditions that were imposed.

After the hearing, Tobias Garnett, a human rights lawyer working with XR’s legal strategy team, said: “We’ve had a good day in court today, where our lawyers have been defending the right to peaceful protest and our ability to ensure those in power are able to hear the uncomfortable truth about the climate and ecological emergency.

“Rather than wasting its time and money on attempts to silence protest, the government should focus its efforts on meaningful action against the biggest threat we face.”

Earlier, Garnett had said that more than 400 people may have been arrested under the terms of the London-wide section 14. “It means there are a couple of hundred people whose arrests were maybe unlawful,” he said. “That means they might have a cause of false imprisonment.”

Police made the order on Monday evening last week, during XR’s second week of protests in the capital. Some activists linked the imposition of the order to their targeting of the financial district earlier that day. It had the effect of banning all assemblies of two or more XR activists within the Metropolitan and City of London police force areas for the remainder of the week, although supporters continued to gather, hold protests and carry out direct action until Friday.

The application for judicial review was brought on behalf of XR by Jenny Jones, Caroline Lucas and Ellie Chowns of the Green party, the Labour MPs Clive Lewis and David Drew, the Labour activist Adam Allnutt and the Guardian environment writer George Monbiot.

Lucas said: “The police use of a section 14 order to ban all Extinction Rebellion protests across the whole of London was a huge overreach of police powers.

“This power is there to help the police manage protests, not shut them down altogether. Extinction Rebellion are carrying a message we all need to hear. They won’t be silenced by a police crackdown, nor should they be in a free democratic society.”

A decision is expected next week.