Kevin McCarthy faces an ethics complaint after allegedly elbowing a fellow Republican lawmaker in the back on Capitol Hill

Former US House Speaker Kevin McCarthy has allegedly assaulted one of the Republican colleagues who voted last month to oust him from his powerful position, leading to an ethics complaint from the ringleader of the internecine revolt.

The incident was said to have occurred on Tuesday, while Representative Tim Burchett was speaking with NPR reporter Claudia Grisales in a US Capitol hallway, following a closed-door meeting of GOP lawmakers. Burchett, a Tennessee Republican, said McCarthy elbowed him in the back as he walked behind him. Grisales said she saw McCarthy shove Burchett from behind, causing Burchett to lunge toward her. 

Burchett can be heard reacting to the alleged jab in an audio clip of the incident. At one point, he followed McCarthy down the hallway and asked the ex-speaker why he hit him in the back. McCarthy denied elbowing him, at which point Burchett said, "You've got no guts. You did so ...  the reporter said it right there. What kind of chicken move is that? You're pathetic, man."

Burchett later told reporters that McCarthy was protected by his bodyguards after the painful jab, which he called a "clean shot to the kidneys." He said he believes the incident was retribution for his decision to vote with seven other Republicans to remove McCarthy as speaker - the first such ouster in US history.

"A guy throws a rock over the fence when he was a kid and runs home and hides behind his momma's skirt," Burchett said. "He's got his security detail around. He knows nobody's gonna do anything to him."

McCarthy, a California Republican, denied that he shoved or elbowed his colleague, telling CNN that the hallway in which he passed behind Burchett was cramped. 

Representative Matt Gaetz, the Florida Republican who led the campaign to replace McCarthy as House speaker, filed an ethics complaint following the alleged assault.

"This Congress has seen a substantial increase in breaches of decorum unlike anything we have seen since the pre-Civil War era," Gaetz wrote in his complaint. "I myself have been a victim of outrageous conduct on the House floor as well, but nothing like an open and public assault on a member, committed by another member. The rot starts at the top."

The alleged incident came on the same day on which a US senator nearly came to blows with a witness during a committee hearing. Oklahoma Republican Markwayne Mullin confronted Teamsters president Sean O'Brien about a social media post in which the union official accused the senator of playing a "tough-guy act" and challenged him to a fight "any place, any time, cowboy."

"Sir, this is the time, this is the place, if you want to run your mouth," Mullin said. "We can be two consenting adults; we can finish it here." 

"OK, that's fine. Perfect. I'd love to do it right now," O'Brien replied.

When Mullin stood up and began moving toward O'Brien, Senator Bernie Sanders, the Vermont independent who chairs the committee, intervened to prevent a brawl.

"This is a hearing," Sanders said. "And God knows the American people have enough contempt for Congress. Let's not make it worse."

Mullin, a businessman who was sworn in as a senator earlier this year, fought and won three MMA fights in 2006 and 2007.