Just Stop Oil has said a lorry crash that injured a police officer was an “awful situation” as the group staged its third day of protests along the M25.
The incident has led to road closures between J26 and J27 clockwise, causing delays during the early rush hour on Wednesday.
Officers are also at J30 of the M25, where one Just Stop Oil protester climbed a gantry, with one person stopped.
“The collision of two lorries and the injury of a police officer on the M25 this morning is an awful situation. The level of disruption being witnessed on the M25 should not be happening - people are rightly angry and frustrated,” Just Stop Oil said in a statement.
The statement added: “The impact on people’s lives is huge. In normal circumstances, this would be unacceptable. It should never have come to this.
“The failure of our politics has left us with no other option as we seek to protect our rights and freedoms from a collapse in law and order due to a heating world.”
Chief Superintendent Simon Anslow, of Essex Police, praised the officers on the scene.
“One of our officers has been injured as they worked to help resolve this situation. Our roads policing officers are dedicated, specialist officers who come to work to serve the public and keep you safe on our roads. They do this tirelessly, day-in day-out.
“Sadly, this morning one of these fantastic officers has been injured while carrying out this work. My thoughts are with them and their family.”
Essex Police were unable to stop an estimated 10 protesters climbing the overhead structures, despite patrolling the area.
The protesters for the JSO climate change group are demanding the government stops all new oil and gas licences.
Isabel Rock, 41, an artist from South London, is one of the activists up the metres-high structures. She said: “I'm doing this for my baby nephew and his unborn sister.”
Just Stop Oil said around 10 of its supporters climbed onto gantries in “multiple locations” on the M25 from 6.30am on Wednesday, in what is the third consecutive day of protests on the UK's busiest motorway.
They have been joined by activists from Animal Rebellion, a group campaigning for “a plant-based food system”.
According to Just Stop Oil, its supporters have been arrested more than 2,000 times since its campaign began on 1 April, and 15 are currently in prison.
