Insulate Britain has warned that the M25 will become a “place of non-violent civil resistance” on Wednesday.
The road-blocking climate group urged motorists to avoid the motorway from 7am or cut their speed to 20mph “to minimise the risk of accidents”.
It said this is in response to Government-owned National Highways securing a new court injunction banning activities that obstruct traffic on its 4,300-mile network of motorways and major A-roads in England.
This is the fourth injunction taken out in response to Insulate Britain’s protests.
Activists have blocked roads on 15 days since September 13, causing misery for drivers stuck in long queues of traffic.
Protesters have frequently targeted the M25, which is the UK’s busiest motorway.
Insulate Britain said in a statement: “We are not concerned with endless injunctions. We are not concerned with our fears. We are concerned with fulfilling our duties and responsibilities at this ‘period of consequence’.
“Starting from 7am on the morning of Wednesday 27th October, the M25 will become a place of non-violent civil resistance to stop our Government committing crimes against humanity.”
The group – an offshoot of Extinction Rebellion – wants the Government to insulate all UK homes by 2030 to cut carbon emissions.
The statement urged National Highways to enforce a 20mph speed limit on the M25 to “keep the public safe”.
It also called on the police to “refuse to arrest us, as we are upholding the British constitution and they have a duty to refuse to obey any Government that fails to uphold its first and most important responsibility: the protection of people in Britain”.
People who break injunctions can be found to be in contempt of court, which carries a maximum penalty of two years in prison or an unlimited fine.
But prosecutions for this offence usually take several months.
The Department for Transport said on Tuesday that more than 100 Insulate Britain activists have been served with court papers in relation to the injunctions.
Transport Secretary Grant Shapps said: “We are making use of every avenue of existing law to try to prevent the continued life-endangering action being carried out by Insulate Britain, which is causing intolerable disruption to motorists’ lives and livelihoods.
“This new interim injunction will ban activities that obstruct motorways and major A-roads across the entire country.
“On top of the immediate measures we’re taking, the long-term solution lies in the changes to the Police, Crime, Sentencing and Courts Bill which were set out by the Home Secretary, giving additional powers against disruptive protests which target critical national infrastructure.
“This includes unlimited fines and prison sentences of up to six months for obstructing highways.”