A radio journalist said she was handcuffed and detained by police for five hours after she was 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 Police Chief Charlie Hall said measures were now in place for legitimate media to do their job.
Ms Lynch said the incident was “absolutely terrifying”.
It comes after a photographer and filmmaker said they were detained by police for around 13 hours after trying to cover the protests earlier this week.
Other protests took place on Wednesday.
She said the arrest happened on a bridge between junction 20 (Abbots Langley) and junction 21 (M1/St Albans junction).
Ms Lynch said she showed officers her press card and explained she was reporting on the protest, but her phone was taken and she was arrested.
She said she was searched at the side of the road, before officers seized her devices and took her to Stevenage Police Station in a guard van.
She said: “This journey took over an hour due to the closure of the M25.
“I was in the back of a police van, I had my hands in front of me, handcuffed all the time, all alone, the two policemen were behind the glass cage.
“That’s when I realized ‘gosh, I could be charged here’ and it all goes through your mind ‘did I actually commit this offence?’ even though I knew not.
“We arrived at the police station and I thought I would answer their questions and be on my 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 cushion for a bed in one corner and a metal toilet in the other,” she said.
“I was just doing my job. What’s also terrifying is what this means for freedom of the press. It was blindingly obvious that I was a journalist.”
A statement from Hertfordshire Police said: “Our officers have been instructed to act as quickly as possible, using their professional judgement, to weed out any possible protesters in order to restore roads and prevent anyone from hurt.
“However, Police Chief Charlie Hall acknowledges the concerns over recent arrests of journalists who have arrived at these locations and been present with protesters at the scene. Additional measures are now in place to ensure that legitimate media are able to do their job.
“Furthermore, Mr Hall is today calling for an independent force to review our approach to these arrests and identify any lessons we should learn from handling these difficult situations.”