Police have claimed it is “very difficult” to bring charges against environmental activists after 27 members of Insulate Britain were arrested for blocking a roundabout at a junction with the M25.

Lisa Townsend, Surrey’s police and crime commissioner, said the police were receiving “an enormous amount of flak” over their response but she insisted officers were “doing their utmost to prevent the disruption”.

It comes after the same junction was targeted twice in six hours. On Wednesday morning, police arrested 11 people who had glued themselves to the road on a roundabout at junction 3, the Swanley Interchange in Kent, at about 7.30am.

The group returned at 1pm when a further 16 arrests were made for the same offence. All 27 people are being held in custody.

Insulate Britain, which is calling on the government to insulate all UK homes by 2030 to cut carbon emissions, has continued to block the M25 despite the government obtaining an injunction prohibiting protesters from doing so.

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

But Townsend said: “It has been very difficult for the police because if they charge the protesters with a relatively minor offence, it is likely to be discontinued.

“If they try to elevate the charge to a more serious one, they are finding it is not reaching the necessary threshold.

“The public deserves to see a response from all parts of the criminal justice system and it is unfair for the police to be blamed if people do not end up before the courts.”

Insulate Britain, an offshoot of Extinction Rebellion, said in a statement: “We are going nowhere. You can raid our savings. You can confiscate our property. You can deny us our liberty and put us behind bars.

“But shooting the messenger can never destroy the message: that this country is going to hell unless you take emergency action to stop putting carbon into the air. Boris get on with the job.”

Wednesday was the seventh day that the group has targeted the M25.

The activists have become noted for their tactic of blocking London’s orbital motorway and other major roads as they try to draw greater attention to the climate crisis. Specifically, they have called for ministers to fully insulate all homes in the UK within a few years.

They argue that the act would not only reduce the UK’s climate emissions, it would also help tackle fuel poverty, which the latest official figures show affects more than 3m households in England alone.

Last Tuesday, the high court granted an injunction preventing protesters from disrupting traffic on to or along the M25 after several protests. The activists also targeted roads leading to Dover and a judge granted a further injunction last week. The activists claimed the campaign, which entered its third week on Monday, has been carried out by 115 people and resulted in more than 400 arrests.

While Insulate Britain’s methods have been heavily criticised by some, academics and policy experts have suggested there is support for the end the activists seek.

Experts have seen properly insulating homes as “low-hanging fruit” in the effort to reduce the UK’s carbon emissions. Last week, Jess Ralston, an analyst at the Energy and Climate Intelligence Unit, told the Guardian a 2017 study had found the initial cost of the work would be dwarfed by the financial and social benefits it brought.

Kent police tweeted: “The Swanley Interchange roundabout at J3 of the M25 has now reopened following an earlier protest, which has resulted in us arresting 11 people. Delays remain in the area whilst the backlog of traffic clears. Thank you for your patience.”

Activists welcomed a pledge by the Labour leader, Sir Keir Starmer, to insulate every home that needs it in Britain over the next decade. One woman glued to the road said: “That’s excellent news. Let’s get the Labour party in. “It would cut UK emissions by 15%, it’s the easiest thing to do.”

Another woman added: “When will the Conservatives do the same thing?”

As well as targeting the London ring road, protesters have blocked other important routes including the A1(M) and A20 near the Port of Dover.