Protests blocking the M25 are “illegal” and police must act more quickly to stop them, the Transport Secretary said as dozens more demonstrators were arrested.

Environmental protesters from Insulate Britain targeted the M25 for a fourth time in little more than a week on Monday, blocking slip roads by gluing themselves to the carriageway and pouring paint on to the roads as part of their campaign to improve home insulation.

The group said many of the people involved in Monday’s protests were involved in three similar demonstrations last week across junctions in Kent, Essex and Surrey.

Protestors targeted M25 junctions are Brentwood and Lakeside, as well as the M11 near Stansted. 

Police have come under pressure from the Government to clamp down on the protests and limit disruption while one minister said the protests are “irresponsible” and “dangerous”.

Grant Shapps told the PA news agency: “I think it’s irresponsible, I think it’s dangerous.

“It’s completely counterproductive as well because they’re actually creating the pollution they want to get rid of by having cars standing still, so there’s no justification for that kind of action.

“I call on them to stop and the police to intervene.”

Asked if he wants the police to take a more robust approach to the demonstrations, Mr Shapps said: “The police will have to work out their approach and tactics, but it’s not right for our roads to be blocked for illegal protests like this to take place, and for it to happen repetitively.

“I’ve no doubt at all the police will want to learn from their experience and make sure they’re able to step in more quickly and efficiently.”

Hertfordshire Constabulary were called to junction 18 near Chorleywood of the M25 at 8.12am and found “several” protesters glued to the carriageway. They arrested 13 people and the road has now been reopened.

Officers were called again three minutes later to reports of protesters near junction four, the Stanborough Interchange, of the A1M where a diversion was put in place.

A total of 16 people were arrested there, where the majority had glued themselves to the road, before police reopened the carriageway.

Images taken at the scene show people being searched and blue paint splattered across the road, with the words “Insulate Britain” and a heart also painted.

CCTV motorway traffic cameras of the M25 anticlockwise at J18, the Amersham and Watford turn-off, showed traffic piling up across the three lanes shortly before 8.40am on Monday.

Chief Superintendent Nick Caveney said officers were on the scene “within minutes” and the protesters were now in custody.

He said: “Protesters have made it clear that they intend to continue causing disruption. Not only is purposely blocking a highway incredibly dangerous, it also affects thousands of members of the public who are stuck in delays as a result.

“We have robust plans in place in order to minimise any disruption and to allow us to make arrests as quickly as we possibly can. This includes, but is not limited to, monitoring areas that have been identified as possible protest targets.

“I understand and appreciate the frustration regarding the considerable delays and inconvenience that has occurred as a result of the protests.

“We have now made a total of 76 arrests in relation to protest activity across Hertfordshire over the last week.”

A statement from the protest group said: “Early this morning, Insulate Britain blocked the M25 for a fourth time.

“Actions will continue until the Government makes a meaningful commitment to insulate all of Britain’s 29 million leaky homes by 2030, and all social housing by 2025.

“Many of those blocking the roads today have participated in all four actions to date.”

The group wrote to National Highways and the police on Sunday to urge for speed limits to be reduced and to alert them to the action on Monday.