Tory chief Lee Anderson became embroiled in an "aggressive" row with expelled Conservative Andrew Bridgen and the father of Game of Thrones star Rose Leslie in a Commons restaurant.
The controversial deputy chairman was said to have told 69-year-old ex-Tory councillor Sebastian Leslie to "come outside and we'll sort it out" in a row over Mr Bridgen being kicked out of the party.
The altercation came shortly after Mr Anderson locked horns with Metropolitan Police Commissioner Sir Mark Rowley during a committee hearing, when the Met chief schooled him on policing Extinction Rebellion protests.
Mr Bridgen and Mr Leslie were having lunch in Parliament's Portcullis House shortly after it emerged Mr Bridgen had been kicked out by the Tories for comparing Covid vaccines to the Holocaust.
The pair told PA they became embroiled in the argument with Mr Anderson after seeing him having lunch with friends in the Adjournment restaurant.
Mr Bridgen was angered by his expulsion being made public while he still has time to appeal against the decision.
Mr Leslie, whose daughter Rose Leslie played Ygritte in Game Of Thrones, said he told the party deputy, "Hold on Lee" because "he was being so bloody rude to Andrew".
"He turned to me and said, 'Hold on grandad, come outside and we'll sort it out'," Mr Leslie said.
As a chieftain of the Scottish clan Leslie, he asked Mr Anderson whether he wants to use "pistols or claymores?", which he explained was a reference to ancient traditions of duelling.
"He was aggressive and out of control," Mr Leslie, a grandfather-of-six, added. "It was very threatening and aggressive."
Mr Leslie, who was suspended from the Tories in 2018 over council tax payments, said he did not plan to make a complaint despite believing the MP was "extremely rude" and "obviously bloody angry".
But Mr Anderson said Mr Bridgen had been "rude and aggressive" as he lunched with two friends.
"I was having lunch with two friends when a very angry looking Andrew Bridgen walked over with his friend," the MP for Ashfield said.
"Andrew spoke briefly to one of my guests who he knew but then turned his attentions to me in a rude and aggressive manner.
"I literally had no idea what he was talking about and then both men left. After apologising to my guests for the outburst I then walked over to Mr Bridgen's table to express my disapproval."
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