Around 40 members of the movement, an offshoot of Extinction Rebellion, blocked two strategic locations during rush hour on Friday: Junction 25 of the M25 at Waltham Cross, Hertfordshire and the A501 at Old Street roundabout in Islington, North London.
The environmental activists renewed their call for the UK government to insulate millions of homes, a move that would reduce carbon emissions. They said Prime Minister "Boris Johnson should be taken to court for treason", and that people are being "tossed aside as expendable".
Footage uploaded to Twitter showed members of the group lying down on the road in front of vehicles at Junction 25, with police attempting to drag the protestors away.
While one image purported to show a children's intensive care ambulance unable to get past and reach its call, Insulate Britain claimed that it has a "blue lights policy", under which it allows emergency service vehicles to proceed.
Another video from Old Street showed police arresting several members, with some even having to be hoisted off the road by multiple officers before being detained.
Friday's protests, the twelfth rally the group has staged so far, come after UK Home Secretary Priti Patel announced earlier this week that the maximum penalties for disrupting motorways would be increased and that Downing Street would "criminalise interference with key infrastructure such as roads, railways and our free press."
Insulate Britain, however, issued a counter statement on Wednesday declaring, "We remain more fearful of the loss of our country than we do of the Home Secretary."
"The law can be changed, punishments increased, our savings raided, we face being imprisoned. But shooting the messenger can never destroy the message: our country is facing the greatest risk ever and our government is failing us", the notice read.
Johnson hit out at the group on Tuesday, denouncing the protests' legitimacy and slamming the members as being "irresponsible crusties who are basically trying to stop people going about their day's work and doing considerable damage to the economy."
Downing Street has previously defended its existing insulation policies, remarking that it was “investing £1.3 billion this year alone to support people to install energy efficiency measures.”