Twenty-three people have been arrested after Just Stop Oil protesters climbed gantries on the M25 despite a major Metropolitan Police operation to foil their plans.

Assistant Commissioner Matt Twist branded the demonstrations as “criminality” with the intention of disrupting thousands of people’s lives.

Speaking to journalists on Monday, he said: “This isn’t protest, this is criminality where people are taking extremely hazardous steps disrupting the M25.

“This action is grossly disproportionate to any legitimate aim that this group may have. This is criminality and we’ll treat it as such.”

The Metropolitan Police arrested seven people before Monday’s protest on suspicion of “conspiracy to intentionally or recklessly cause public nuisance”, a new offence under the Police, Crime, Sentencing and Courts Act 2022 that carries a maximum penalty of 10 years in prison.

“We suspected that the intent of the individuals involved was completely disproportionate to any legitimate right to protest,” Mr Twist said.

But the protest went ahead, with forces including Kent, Essex, Surrey and Hertfordshire facing demonstrators in 13 locations.

Surrey Police tweeted that they had reports of protesters at a number of places along the motorway, resulting in temporary lane closures, while Essex Police said arrests were made after reports of people climbing up an overhead gantry close to junction 30 of the M25.

Hertfordshire Police said five people had been arrested after protesters attempted to climb overhead gantries at various junctions.

The motorway, England’s busiest, was cleared by Monday afternoon, Mr Twist said.

As well as the arrests, police believe that some of those involved in the demonstrations could have breached a High Court injunction obtained by the Highways Agency.

Just Stop Oil has vowed to continue its action, saying it will demonstrate “every day” until the group’s demand for no new oil and gas in the UK is met.

In an update on its website, the group said: “This is not a one-day event, expect us every day and anywhere. This is an act of resistance against a criminal government and their genocidal death project.

“Our supporters will be returning – today, tomorrow and the next day – and the next day after that – and every day until our demand is met: no new oil and gas in the UK.”

According to the Met, which is conducting the operation in conjunction with the National Police Coordination Centre (NPoCC), more than 10,000 officer shifts have been dedicated to policing Just Stop Oil protests since the start of October.

Police remove activists from Just Stop Oil during their protest on Cromwell Road, London, near to the Victoria & Albert Museum October 19, 2022
Police remove activists from Just Stop Oil during their protest on Cromwell Road near the Victoria & Albert Museum (Aaron Chown/PA)

Police are calling on the public to assist with preventing public disruption from protesters by reporting it to 999.

Essex Police said it was “dealing robustly” with protesters and urged the public not to intervene.

Just Stop Oil staged 32 days of disruption from the end of September and throughout October, which the Met said resulted in 677 arrests with 111 people charged, and officers working a total of 9,438 additional shifts.

The climate change action group has been calling on the Government to abandon plans to licence more than 100 new oil and gas projects by 2025, and to do more to help people with their skyrocketing energy bills.

Police officers deal with activists from Just Stop Oil during their protest outside Harrods department store in Knightbridge, London on Thursday October 20, 2022
Police officers deal with activists from Just Stop Oil during a protest outside Harrods department store in Knightsbridge, London (Ian West/PA)

According to the group, since its campaign began on April 1, Just Stop Oil supporters have been arrested nearly 2,000 times, and five are currently in prison.