Nigel Farage had milkshake thrown at him during a campaign walkabout.
The Brexit Party leader had just given a short speech in Newcastle as part of a tour of the country ahead of the European elections.
A man was dragged away by a police community support officer and later seen in handcuffs.
Paul Crowther, 32, from Throckley, Newcastle, said it was a £5.25 Five Guys banana and salted caramel milkshake.
Mr Farage was campaigning in the North East ahead of polling day on Thursday.
A Northumbria Police spokesperson said: “A 32-year-old man has been arrested on suspicion of common assault and remains in police custody.”
Mr Farage is the the latest victim of a protest which has seen other European election candidates such as Ukip’s Carl Benjamin and ex-English Defence League leader Tommy Robinson suffer similar attacks.
Shortly afterwards, Mr Farage could be heard saying “how did you not stop that?” as his staff ushered him away from the scene.
He tweeted: “Sadly some remainers have become radicalised, to the extent that normal campaigning is becoming impossible.
“For a civilised democracy to work you need the losers consent, politicians not accepting the referendum result have led us to this.”