The Prime Minister has described the video footage that emerged of MP Mike Amesbury appearing to punch a man to the ground as “shocking”.
Amesbury has been suspended from the party and has had the Labour whip withdrawn after the CCTV and mobile phone footage appeared on Sunday.
Sir Keir Starmer said the party had “moved very swiftly” to respond.
He added: “There is now a police investigation and in the circumstances you’ll appreciate there’s not much more I can say about that.”
Cheshire Police said a 55-year-old man had been voluntarily interviewed under caution in relation to the incident and was later released pending further inquiries.
Amesbury has been contacted for comment.
Posting on his own Facebook page on Saturday, the backbencher said: “Last night I was involved in an incident that took place after I felt threatened following an evening out with friends.
“This morning I contacted Cheshire Police myself to report what happened.
“I will not be making any further public comment but will of course cooperate with any inquiries if required by Cheshire Police.”
In a statement issued before the Daily Mail footage emerged, Cheshire Police had said they were “called to reports of an assault in Frodsham” at 02:48 BST on Saturday 26 October.
“A caller reported he had been assaulted by a man in Main Street. Enquiries are ongoing,” the police added.
In footage obtained by the Daily Mail, the Runcorn and Helsby MP is apparently seen continuing to hit the man as he lies in the street.
A different video, posted on X, purported to show Amesbury shouting and swearing at the man lying in the street in Frodsham, Cheshire.
In the initial clip, Amesbury can be heard shouting: “You won’t threaten the MP ever again, will you?”
‘Questions to answer’
A Labour Party spokesman 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.”
A Conservative Party spokesman said Amesbury “has questions to answer about his actions”, adding that it was “right they are thoroughly investigated”.
A spokesperson for Reform UK – whose candidate came second behind Amesbury in July’s general election – called for him to resign.
The MP was first elected to the Commons in 2017 representing Weaver Vale.
In the last election he was selected for a redrawn constituency of Runcorn and Helsby.
He was elected in the July general election with a majority of 14,696.
A former shadow housing minister, he is currently a member of two Commons committees – the Housing Communities and Local Government Committee and the Modernisation Committee.
In July 2023, a 56-year-old man was found guilty of stalking and harassing Amesbury at his constituency office and in town.
The Manchester-born MP is a former careers adviser and has worked with Deputy PM Angela Rayner and Greater Manchester Metro Mayor Andy Burnham.