The climate activists moved into lanes of traffic on Tuesday morning, forcing cars to come to a stop.
It was the fifth time the group, which is calling on the government to help insulate homes to reduce emissions, has blocked the M25 since last week.
Police said 23 arrests were made in connection with the incident on a stretch of Britain’s busiest motorway in Surrey.
A video shows protesters walking onto the main carriageway, carrying signs and sitting on the ground.
On the other side of the motorway, more protesters are seen sat down holding a banner.
Officers dragged activists off the road as traffic built up.
Surrey Police said around 8.30am on Tuesday that the affected stretches of road between Junctions 9 and 10 were fully re-opened after officers cleared all Insulate Britain activists off the road.
The force said they were called around half an hour earlier following reports of protesters on both carriageways.
It said they found “a number” of demonstrators at the scene, where they had also poured blue paint on to the motorway.
Insulate Britain confirmed they led the demonstration, adding that new people have joined their campaign to improve home insulation in addition to the others who have been involved in similar demonstrations in Hertfordshire, Kent, Essex and Surrey over the past week.
It added that the recent rise in gas and electricity costs has “increased the urgency” for change and they would end their campaign as soon as they hear a “meaningful commitment” to their demands.
“The idea that people would suddenly decide insulating our leaky homes is a bad idea as a result of our campaign is frankly laughable,” Liam Norton, a spokesperson for the group, said.
He added: “The people of Britain understand that climate change is a severe threat to everything they hold dear. They are looking to the government for leadership.
“We have a practical solution and have received encouragement for our aims from many construction industry professionals. “
Insulate Britain protesters have blocked parts of the M25 multiple times in just over a week, including junction 18 on Monday.
Additional reporting by Press Association
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