Environmental activists blocking the M25 face possible imprisonment after National Highways was granted an injunction against the protests, Transport Secretary Grant Shapps said.
Campaign group Insulate Britain has shut down parts of the M25 five times in just over a week.
Mr Shapps wrote on Twitter: “Invading a motorway is reckless and puts lives at risk.
“I asked National Highways to seek an injunction against M25 protestors which a judge granted last night.
“Effective later today, activists will face contempt of court with possible imprisonment if they flout.”
Home Secretary Priti Patel said the “important injunction” means “people can get moving again” on the M25.
“We will not tolerate lives being put at risk,” she said.
“Those who continue to do so risk imprisonment.”
Surrey Police arrested 38 activists from the group on Tuesday who had targeted junctions nine and 10 of Britain’s busiest motorway.
Footage taken at the scene by LBC showed the protesters walking on to the motorway and sitting down on the ground in front of moving traffic.
Some then held up banners reading “Insulate Britain” and poured blue paint on to the road, before they were dragged away by officers.
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