Congressman Matt Gaetz escalated his personal feud with a former House speaker, Representative Kevin McCarthy, on Wednesday, filing an ethics complaint that accuses his nemesis of elbowing a colleague in the back. 

On Tuesday, Mr. McCarthy allegedly elbowed Congressman Tim Burchett in his kidney while brushing by him in the basement of the Capitol. Mr. Burchett was one of the Republicans to vote to oust Mr. McCarthy.

Mr. McCarthy maintains that he only accidentally bumped into Mr. Burchett in a part of the Capitol basement where the hallway narrows.

“If I hit somebody, they would know it,” Mr. McCarthy told reporters. “If I kidney punched someone, they would be on the ground.”

An NPR reporter, Claudia Grisales, witnessed the incident, saying in a tweet that Mr. McCarthy “shoved” Mr. Burchett, adding, “I thought it was a joke, it was not. And a chase ensued.”

“Burchett responded jokingly as McCarthy kept walking, ‘Sorry Kevin didn’t mean to elbow —’ then seriously yelled, ‘Why’d you elbow me in the back Kevin?! Hey Kevin, you got any guts!?’” Ms. Grisales reported.

Mr. Burchett has since doubled down on his characterization of the incident, telling CNN, “It’s disappointing that’s the way he will end his career — spiraling out of control.”

“And it’s disappointing because we should be dealing with the budget and all these other things I said that are really in a crisis stage right now, and people like himself, it’s all about them and their childish activities,” Mr. Burchett said.

Now, Mr. McCarthy’s chief antagonist, Mr. Gaetz, is rubbing salt in Mr. McCarthy’s wounds, filing an ethics complaint against him over the incident.

“Needless to say, this incident deserves immediate and swift investigation by the Ethics Committee,” Mr. Gaetz wrote in a letter. “This Congress has seen a substantial increase in breaches of decorum unlike anything we have seen since the pre-Civil War era.”

Mr. Gaetz added, “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.”

Mr. Gaetz’s ethics complaint comes after he led a successful charge early last month to oust Mr. McCarthy as speaker, the culmination of a highly personal feud. In the preceding months, Mr. McCarthy had refused to end an ethics investigation into Mr. Gaetz involving alleged sexual dalliances — which Mr. Gaetz has denied — with a 17-year-old girl. 

Following his ouster as speaker, Mr. McCarthy told CNN that the GOP would benefit “tremendously” if Mr. Gaetz were to exit Congress. 

In the interview, Mr. McCarthy referenced the ongoing ethics investigation against Mr. Gaetz stemming from his friendship with a disgraced Florida tax collector, Joel Greenberg, who pleaded guilty last year to a laundry list of federal crimes, including identity theft, stalking, wire fraud, bribery, and paying a 17-year-old girl to have sex with him and other men.

In 2018, Mr. Gaetz paid Greenberg $900 over two payments, with the first payment labeled “test” and the second labeled “hit up ___,,” with the blank space being the redacted name of a teenage girl, according to the Daily Beast, which reviewed the Venmo histories of the men before they were made private.

Greenberg later sent $900 across three payments to three girls labeled as “tuition,” “school,” and “school.” These payments eventually sparked an FBI probe, which closed without investigators bringing charges.

Regarding the matter, Mr. Gaetz said that “the last time I had a sexual relationship with a 17-year-old, I was 17.”

In the House, though, an Ethics Committee investigation continues into Mr. Gaetz’s relationship with Greenberg and the girl. Mr. McCarthy, during his time as speaker, refused to end the investigation after Mr. Gaetz had fervently led opposition to his election as speaker. 

In his remarks to CNN, Mr. McCarthy alleged that Mr. Gaetz’s crusade against him was rooted in the Ethics Committee investigation, saying Mr. Gaetz’s problem with Mr. McCarthy was “more personal” than disagreeing with his politics.

“If the Ethics Committee never does anything to Gaetz, then Gaetz was successful in stopping what probably should rightfully come to him,” Mr. McCarthy said.