MP Mike Amesbury has lost the Labour whip after a video emerged appearing to show him punching a man to the ground.
The party said the Runcorn and Helsby MP had been suspended “pending an investigation” into the incident.
It comes after footage obtained by the Mail Online appeared to show Mr Amesbury, 55, repeatedly hitting another man as others nearby shout “stop it”.
A Labour spokesperson said: “Mike Amesbury MP has been assisting Cheshire Police with their inquiries following an incident on Friday night.
“As these inquiries are now ongoing, the Labour Party has administratively suspended Mr Amesbury’s membership of the Labour Party pending an investigation.”
Cheshire Police confirmed a 55-year-old man had been voluntarily interviewed under caution in relation to the incident after officers were called to reports of an attack in Frodsham at 2.48am on Saturday.
“He has since been released pending further inquiries,” the force said.
CCTV published on Sunday captured two men standing facing each other before the man purported to be Mr Amesbury punched the other and continued hitting him on the ground.
It is not clear from the video what happened in the moments beforehand.
It comes after different footage posted on social media on Saturday appeared to show the MP shouting and pointing his finger at a man lying in the street in Frodsham, Cheshire.
“You won’t ever threaten me again, will you? You won’t ever threaten me again,” he appeared to say.
Mr Amesbury said he will “co-operate with any inquiries” but was “determined to remain an open and accessible MP for our community” after the initial footage circulated online.
He said in a statement: “Last night, I was involved in an incident that took place after I felt threatened on the street following an evening out with friends.
“This morning, I contacted Cheshire Police myself to report what happened during the incident.
“I will not be making further public comment but will, of course, co-operate with any inquiries if required by Cheshire Police.”
In July last year, a 56-year-old man was convicted of stalking the MP at his constituency office in Frodsham, where prosecutors said he was seen staring through the glass and asked guards about their level of security.
Tory leadership candidate Robert Jenrick wrote on X, formerly Twitter: “Labour’s promised to ‘smash the gangs’. Looks like they’re now smashing their constituents instead.”
Reform UK called for him to resign so that a by-election could be held in his seat.
The party came second in the constituency at the general election with 7,662 votes to Mr Amesbury’s 22,358.
A Reform spokesperson said: “The new footage of Mike Amesbury MP is damning. No matter what verbal exchanges happened before, it’s never acceptable for anyone to resort to violence to solve a dispute, let alone a sitting Member of Parliament.
“It’s quite clear that the people of Runcorn and Helsby deserve far better than this.
“Reform UK are today calling for Mike Amesbury to do the honourable thing and resign immediately so a by-election can be held.”