Police officers are under so much pressure to quickly remove climate activists blocking the M25 that they are “putting their lives at risk”, Scotland Yard’s Deputy Commissioner said.

Sir Stephen House insisted officers are taking action “incredibly quickly” against Insulate Britain.

He told the London Assembly’s Police and Crime Committee: “If I’m frank, I worry that we are under pressure to do it so quickly that officers are putting their lives at risk.

“The most recent one I saw had officers running between articulated lorries that were moving on the main carriageway of the M25.

“We cannot be doing that. We cannot put people’s lives at risk. My officers’ lives at risk and indeed the demonstrators’ lives at risk.

“We have to look out for that first.

“But we have been very quick in moving these people and arresting them.”

He added: “They started off on the slip roads, which is bad enough, but we’ve now moved on to the main carriageways of the M25, which is absolute lunacy.”

Insulate Britain supporters glued their hands to the ground at Junction 30 of the M25 at Thurrock, Essex at around 8am on Thursday.

It was the eighth day the group has targeted the UK’s busiest motorway in the past three weeks.

Essex Police said officers were able to “quickly re-open” one lane, with all lanes open shortly after 10am.

Nine people were arrested on suspicion of obstructing a highway.

An Essex Police spokesman said: “We know this will have been frustrating for drivers caught in the traffic this caused and we want to thank you for your patience and understanding.”

The group, which is calling on the Government to insulate all UK homes by 2030 to cut carbon emissions, said in a statement: “We are raising the tempo this week as, despite the urgency of the situation, there has been no meaningful response from the Government to our demands.

“We are deeply concerned that with rising fuel bills and not enough action on insulation, there will be further unnecessary suffering and deaths among the most vulnerable this winter.”

The group admitted that its actions “are in breach of a High Court injunction” obtained by the Government last week.

The injunction means anyone blocking the M25 could be found to be in contempt of court, which carries a maximum penalty of two years in prison or an unlimited fine.

Transport Secretary Grant Shapps said on Wednesday that “reckless protesters” have “already had knocks on their doors”.

He went on: “We are serving papers and those who continue these idiotic, dangerous and counterproductive demonstrations will be caught and face unlimited fines or prison.”

Insulate Britain said several activists have been contacted at home in relation to the injunction.