Police said 53 Insulate Britain activists have been arrested after they formed a human roadblock on the slip road, at junction 14 near Heathrow, on Monday morning.
They walked into the road about 8am with some being dragged to the safety of the verge by police.
A man sat in the centre of the road was able to glue his hands down to the ground before police could remove him.
It is the sixth timed in two weeks the group has caused disruption on or near the M25.
A Met spokesman said: “ The road has been cleared and traffic is flowing again. We made 53 arrests as we worked to minimise disruption motorists.
“Where possible we opened up lanes to ensure traffic could continue to move. Those arrested are being taken to custody.”
The group, an offshoot of Extinction Rebellion, is calling for the Government to insulate homes in the UK to help cut carbon emissions.
Dr Diana Warner, 62, a retired GP from Bristol who is a member of the group, said she was “determined to do everything she could” to force change.
“I’m here because of desperation, it’s not an easy thing to do,” she said.
“This is the fifth time I’ve been here trying to block a motorway because the only way to get the Government to listen is to disrupt things.
“I’m really sorry, but I’m determined to do everything I can to make us safe and change society … we have to try.”
Victoria Lindsell, 66, a volunteer language teacher, said: “We all understand the frustrations, but this is the only way to make the Government listen.
“We’re incredibly sorry, we’ve all been stuck in traffic jams, but to be inactive is a crime.
“I’m wet through and I’m cold, it’s not my choice but I cannot have the responsibility and not do anything about it.
“People get disrupted in the motorways nearly every day anyway.”
Their controversial tactics have led to National Highways being granted injunctions to prevent people obstructing the M25 and A20 following further demonstrations at the Port of Dover on Friday.
The injunctions mean demonstrators could face time in prison for blocking the routes.
Police have made dozens of arrests since the beginning of the campaign.
Insulate Britain spokeswoman Tracey Mulligan told LBC: “We have certainly got everybody talking about insulation or avoiding the question of insulation.
“We have got people considering that our government is legally failing in their duty to protect us and I think we’re showing that Priti Patel, unfortunately, is trying to scare us with an injunction and that shows her lack of character, not ours.
“You can’t put an injunction on hunger, you can’t put and injunction on physics, and we are terrified for our children’s future and sick of over 8,000 people dying each year from the choice of heating or eating.”
When asked about breaking the injunction, she said: “I wouldn’t say we are happy, we are just putting things into the bigger context. We are tired of over seven million people having to choose between heating or eating and we know that’s going to get worse with the energy crisis that we’re facing now.”