Members of the environmental protest group Insulate Britain have blocked the M25 motorway and a busy central London roundabout, in the group’s 12th disruptive action in four weeks.

According to the climate activist group, about 40 supporters blocked junction 25 of the M25 just before 8.30am on Friday, in defiance of an injunction obtained by National Highways, as well as the A501 at the Old Street roundabout in Islington.

The Metropolitan police said officers were at both scenes, including specialist officers. “We know that some activists have used super glue to frustrate our efforts and to delay Londoners even further,” the force tweeted.

“We train for these scenarios and have specialist teams on hand to help remove people and make arrests.”

For nearly five weeks, Insulate Britain has been conducting an open-ended campaign of disruptive civil disobedience, vowing to continue blocking motorways and other busy roads in and around London until the government agrees to fund the insulation of all homes in Britain, starting with those of the poorest.

In a statement issued on Friday, an Insulate Britain member, Tracey Mallagan, said: “If governments don’t act soon to reduce emissions, we face a terrifying situation. We won’t be worrying about shortages of pasta or loo rolls because law and order breaks down pretty quickly when there is not enough food to go round. The government won’t be wondering if there are enough hospital beds or ventilators, but whether there are enough people left to bury the dead.

“The government is destroying our country. Boris Johnson should be taken to court for treason. Our flesh and blood are being tossed aside as expendable.”

Insulate Britain’s tactics have enraged the government and many members of the public. Speaking on LBC on Friday morning, the transport secretary, Grant Shapps, suggested the protests were counterproductive.

“It’s dangerous, it’s really outrageous, and actually, ironically, it probably adds to pollution as cars idle, waiting for their nonsense … for them to be unglued from the road,” he said.

Shapps called for a “toughening up” of laws to crack down on Insulate Britain’s protests, which he expected would be included in the police, crime, sentencing and courts bill currently before parliament. In the meantime, he said, he had been “applying actively” for court injunctions. “Now these people can go to jail for what they’re doing,” he said.