The chief constable of Hertfordshire constabulary has promised an investigation into the arrests of journalists covering climate protests, amid accusations the force was threatening press freedom and an intervention by Downing Street. After a police officer was injured responding to a third day of protests by the climate activist group Just Stop Oil on the M25 on Wednesday morning, a Hertfordshire constabulary spokesperson said “additional measures” would allow “legitimate media” to cover the protests. Essex police said there had been a collision involving the motorcyclist and 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 said about 10 of its supporters had climbed gantries at various locations. Police in Hertfordshire 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 clear any possible protesters”. “The awful incident in Essex today, where an officer has been injured, underlines this,” the force said. “However, chief constable Charlie Hall recognises the concerns over the recent arrests of journalists who arrived at these locations and have been present with the protesters at the scenes. Additional measures are now in place to ensure that legitimate media are able to do their job,” it added. “In addition, Mr Hall is today requesting an independent force to examine our approach to these arrests and to identify any learning we should take in managing these challenging situations.” The force also said its officers had been told to “conduct full and thorough checks” and seek final approval from a senior before arresting anyone identifying themselves as a journalist. It said an internal review of Charlotte Lynch’s arrest had found that “though the actions of the officers at the scene are understandable, in retrospect an arrest would not have been necessary”. Lynch, a reporter at LBC, on Tuesday became the third journalist arrested in two days by Hertfordshire constabulary while covering Just Stop Oil’s protests. Speaking on LBC on Wednesday morning, Lynch said she had been arrested on suspicion of conspiracy to commit a public nuisance despite being in a public area, some distance from the protesters, and showing officers a valid press ID. Amid an outcry over Lynch’s arrest, Downing Street said the prime minister believed that journalists must be able to do their job freely. Rishi Sunak’s official spokesperson said: “It’s vital journalists are able to do their job freely without restriction. “I am cautious about commenting on specific incidents. Operational decisions are a matter for the police but the prime minister strongly believes in championing press freedoms. We wouldn’t want to see those freedoms impeded whilst journalists are going about their day-to-day business.” Gillian Keegan, the education secretary, told LBC police were wrong to make the arrest. “Journalists shouldn’t get arrested for doing their job,” she said. “We are defenders of free speech.” The area’s MP, Daisy Cooper, wrote a letter to the force criticising it for the “unnecessary and heavy-handed” arrests, which she said “blatantly disregarded the freedom of the press”, before raising the arrests in the Commons. Lynch’s arrest also prompted criticism of police from the National Union of Journalists, the human rights group Liberty and the legal reform group Justice. “This is the second incident in as many days where the police have threatened press freedom and disregarded the right of journalists to cover protests,” said Michelle Stanistreet, the general secretary of the NUJ. “No reporter should fear being placed in a cell for doing their job, and it’s time the police take immediate action to ensure this is prevented in future. We’ve raised this directly with the national police chiefs council and the police forces involved.” Jun Pang, policy and campaigns officer at Liberty, said the arrests were “being enabled and encouraged by the government’s dangerous assault on protest rights”. “The reports we’ve heard of the arrests of journalists are deeply concerning,” Pang said. “Press, film crews and journalists should be able to cover protests without fear of being harassed, having their footage seized or being arrested.” Tyrone Steele, a criminal lawyer at Justice, said: “These incidents clearly demonstrate the broad range of powers that already exist to police protests and show how they can be misused to stifle press freedom. It is vital, and in the public interest, that the press has access to protest sites in order to report on and monitor police powers, essential for preventing abuse.” Lynch’s arrest is thought to be the eighth of a journalist covering actions by Just Stop Oil, whose supporters have been waging a campaign of disruptive protests to force the government into introducing a moratorium on all new oil and gas licences. On Monday, police in Hertfordshire arrested Rich Felgate, a documentary maker, and Tom Bowles, a photographer, also while they were covering protests on the M25.