A radio journalist said she was handcuffed and held in police custody for five hours after being arrested while covering a Just Stop Oil protest.
LBC reporter Charlotte Lynch said she was on a road bridge over the M25 in Hertfordshire on Tuesday.
She said she was arrested on suspicion of conspiracy to commit a public nuisance before being released.
Hertfordshire Chief Constable Charlie Hall said action had now been taken to allow legitimate media to do their jobs.
Ms Lynch said the incident was “absolutely appalling”.
It comes after a photographer and a filmmaker said they were held in police custody for about 13 hours after attempting to cover the protests earlier this week.
More protests broke out on Wednesday.
She said the arrest happened on a bridge between Junction 20 (Abbots Langley) and Junction 21 (M1/St Albans Interchange).
Ms Lynch said she showed officers her press card and said she was covering the demonstration, but her phone was stolen and she was arrested.
She said she was searched at the side of the road before officers confiscated her devices and took her to Stevenage Police Station in a custody van.
She said: “This journey took over an hour because the M25 was closed.
“I was in the back of a police car, my hands were in front of me, handcuffed the whole time, alone, the two police officers were behind the glass cage.
“That’s when it dawned on me, ‘Gosh, I could be charged here,’ and it all goes through your head, ‘Did I actually commit this crime?’ even though I knew I hadn’t.
“We got to the police station and I thought I’d answer their questions and be on our way.”
Ms Lynch said officers wanted to know how she knew about the protest.
She added that she was held in a cell for five hours before being released without further action.
“It was absolutely terrifying to be in a cell with a pad for a bed in one corner and a metal toilet in the other,” she said.
“I was just doing my job. What is also frightening is what this means for freedom of the press. It was obvious that I am a reporter.”
A statement from Hertfordshire Police said: “Our officers have been instructed to act using their professional judgment as quickly as possible to clear any potential protesters in order to get the roads back to service and prevent anyone from being harmed .
“However, Chief Constable Charlie Hall acknowledges the concern over the recent arrests of journalists who have arrived at these locations and were present with the protesters at the site. Additional measures are now being taken to ensure legitimate media can do their jobs.
“Furthermore, today Mr. Hall is calling on an independent force to review our approach to these arrests and to identify any lessons we should learn as we navigate these challenging situations.”
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