Tommy Robinson has been arrested on suspicion of assaulting a man he claims spat in his face.
The former English Defence League leader, 37, was detained after police received reports a man had been attacked at Hollywood Retail Park in Barrow-in-Furness, Cumbria, shortly after 8.30pm on Thursday.
Robinson, real name Stephen Yaxley-Lennon, is also being questioned on suspicion of a public order offence, along with a 43-year-old man from the West Midlands area, a 47-year-old man from the North Wales area and a 28-year-old man from the Bedfordshire area.
Footage shared on social media shows the far-right activist filming himself confronting police officers as they arrive at the scene.
Robinson explains to one of the officers that he “acted in self defence” after someone spat in his face.
In a statement issued on Friday, Cumbria Police said: “Four men from outside the county were arrested last night following a report of an assault.
“Cumbria Police received a call reporting an assault on a man at Hollywood Retail Park, shortly after 8.30pm.
“Officers responded and arrested four men shortly afterwards in the Douglas Street area of Barrow.
“A 37-year-old man from the Bedfordshire area was arrested on suspicion of assault and a public order offence.
“All remain in police custody this morning.
“There were a number of people in the area at the time and officers are keen to hear from anyone who witnessed what happened or the moments immediately before or after.”
Robinson, from Luton, has made two trips to Barrow within the last fortnight and says he is working as a journalist to investigate claims of what he terms may be “a Muslim grooming gang” operating in the town.
Last month Detective Chief Superintendent Dean Holden, of Cumbria Police, said a year-long investigation into “specific allegations of abuse” did not corroborate claims an organisation of Asian men in Barrow were conducting abuse and exploitation against individuals.
He added that police had not “ignored or dismissed” such claims, had taken them seriously and investigated thoroughly.
The statement was issued after allegations of serious sexual abuse and physical violence against a teenage girl, including graphic images of injuries, were shared widely on social media.
Following the 12-month investigation, a 19-year-old woman was charged with several counts of perverting the course of justice.
Tensions have risen in the town in recent weeks, including threats made on social media to a number of Asian takeaways and to a local newspaper reporter.