Responding to Matt Gaetz’s move, Mr McCarthy posted on social media: “Bring it on.” Mr Gaetz retorted: “Just did.”

Tensions between the two Republicans boiled over at the weekend after the Speaker passed a bill with the help of Democrats to fund government agencies. No US Speaker has ever been ousted by such a so-called motion to vacate.

The leadership has two days to bring up the measure for a vote, though procedural tools could be used to thwart the process.

The Speaker is second in the line of succession for the presidency after the US vice-president. He or she sets the lower house of Congress’ legislative priorities, controls committee assignments, and can make or break the White House’s agenda.

The deal late on Saturday that averted a government shutdown left out $6bn (£5bn) of funding for Ukraine because Mr Gaetz, of Florida, and other ultraconservatives insisted the US has spent too much on that country’s war with Russia.

Mr Gaetz has wielded the threat of dethroning Mr McCarthy ever since January when he led party rebels in opposing the California congressman’s bid for the speakership, forcing him to endure 15 gruelling rounds of voting in the chamber.

During the political horse-trading before he ultimately won the gavel, Mr McCarthy agreed to a change of rules that would allow any single lawmaker to call for a vote to oust the Speaker.