Sir Keir Starmer has called footage of a Labour MP punching someone "shocking" - but declined to say if he should resign.
In a video from the weekend Mike Amesbury, the MP for Runcorn and Helsby, was seen punching a man, who fell to the floor, before then hitting him repeatedly.
After the footage came to light, the Labour Party said it had administratively suspended his membership "pending an investigation".
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During a Q&A after a pre-budget speech this morning, Sir Keir sidestepped a question about whether Mr Amesbury should resign as an MP.
"I have seen the video footage, it's shocking," he said.
"We moved very swiftly to suspend him as a member.
"There is now a police investigation and in the circumstances you will appreciate there's not much more I can say about that."
Earlier footage had shown Mr Amesbury shouting at a man while he was lying on the floor, saying: "you won't ever threaten me again".
In a statement the MP said he felt "threatened on the street following an evening out with friends" - and that he "contacted Cheshire Police myself to report what happened during this incident".
"I will not be making further public comment but will, of course, cooperate with any inquiries if required by Cheshire Police," he added.
The latest video showed two men standing facing each other before 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.
Three members of the public could then be seen walking over towards the two men and intervening.
A spokesperson for Cheshire Police said: "A 55-year-old man has been voluntarily interviewed under caution by police in relation to this incident. He has since been released pending further enquiries."
(c) Sky News 2024: Video of Labour MP punching someone is 'shocking', says Starmer
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