Paul Farrelly denies allegations that he was involved in an altercation with fellow Labour MP James Frith after confronting two other colleagues – Ruth Smeeth and Gareth Snell – in a Commons bar.
But a Labour spokeswoman said a number of complaints had been made to the party’s chief whip Nick Brown and Mr Farrelly is now being investigated.
The events are alleged to have taken place after a long debate on the European Union (Withdrawal) Bill which ended at around 11pm.
Mr Farrelly said: “I deny it. I don’t even know who James Frith is.”
Responding to allegations he launched a four-letter outburst at Mr Frith, he said: “That’s not something I would say. That’s absolute nonsense.”
He also said he does not get on with Ms Smeeth and Mr Snell, whose Stoke constituencies border his in Newcastleunder-Lyme.
He added: “The fact we don’t get on is an open secret.”