The home secretary, Suella Braverman, has accused police of failing in their duty and demanded an intensified crackdown on Just Stop Oil activists disrupting the M25 motorway. In a rare move to criticise officers in the midst of an operation, Braverman told police chiefs at their annual conference that she expected “a firmer line to safeguard public order. Indeed, that is your duty.” There has been increasingly disruptive action in the campaign by Just Stop Oil to highlight the climate emergency. Essex police said on Wednesday that an officer riding a motorbike was hurt after a collision with two lorries during a rolling roadblock introduced because of the actions of an activist on London’s orbital motorway between junctions 26 and 27. Just Stop Oil (JSO) said about 10 of its supporters had climbed gantries at various locations, and police said activists had locked their heads on to infrastructure in a new tactic. Hertfordshire constabulary said the protests were causing “significant disruption and potential harm” to the public and that officers had “been instructed to act as quickly as they can, using their professional judgment,” to remove and deter protesters. The force also announced an inquiry after an LBC radio reporter was arrested and held for five hours. The Met commissioner, Sir Mark Rowley, defended police actions, saying chiefs could not place “snipers” in motorway gantries or risk “decapitating” people attaching themselves to infrastructure with bicycle locks. Braverman in her speech labelled those taking direct action as “extremists”, causing “serious disruption to the life of the community”. She said: “Although most police officers do an excellent job, sadly in recent months and years we have seen an erosion of confidence in the police to take action against the radicals, the road blockers, the vandals, the militants and the extremists. “But we have also seen the police appear to lose confidence in themselves – in yourselves. In your authority, in your power. An institutional reluctance. This must change. Criminal damage, obstructing the highway, public nuisance – none of it should be humoured. It is not a human right to vandalise a work of art. It is not a civil liberty to stop ambulances getting to the sick and injured.” She continued: “Such disruption is a threat to our way of life. It does not ‘further a cause’. It is not ‘freedom of expression’, and I want to reassure you that you have my – and this government’s – full backing in taking a firmer line to safeguard public order. Indeed, that is your duty. Scenes of members of the public taking the law into their own hands are a sign of a loss of confidence and I urge you all to step up to your public duties in policing protests.” Rowley appeared to mock demands for even tougher action after a week in which police made pre-emptive arrests. He said: “We have gone as far as we think we can do on the JSO issues. We can’t take snipers, apparently, to people who are on gantries. When we use the angle grinders, we have to apparently just take off the locks, we can’t take off their limbs at the same time. There are limits as to how you can do this at speed.” The Essex chief constable, BJ Harrington, said: “They are hugely dangerous environments to work in. We have been using our powers, we have been making arrests and putting them in front of the courts. Do you want cops physically dragging people out of the way without first trying to persuade or cajole them? If that does not work then you have to be confident to use force and we have been.”