By David Morgan

WASHINGTON (Reuters) -Top U.S. House Republican Kevin McCarthy faced a threat to his speakership on Sunday after a hardline critic within his own party called for a vote to oust him following the passage of a stopgap government funding bill that drew more support from Democrats than Republicans.

Hardline Republican Representative Matt Gaetz told multiple U.S. media outlets he would file a "motion to vacate," a call for a vote to remove McCarthy as speaker, testing McCarthy's support in the House of Representatives, which his party controls by a narrow 221-212 margin.

Gaetz is one of a group of about two dozen hardliners who forced McCarthy to endure a withering 15 rounds of voting in January before he was elected speaker, during which they squeezed out concessions including a rule change to allow any one House member to call for a vote to oust the speaker.

It was not clear how much support McCarthy would have in such a vote, or whether any Democrats would back him. McCarthy angered Democrats last month by launching an impeachment inquiry of President Joe Biden.

"If at this time next week Kevin McCarthy is still speaker of the House, it will be because Democrats bailed him out," Gaetz said in an interview on ABC. "I am relentless and I will continue to pursue this objective."

McCarthy stunned Washington on Saturday when he backed a bill to fund the government through Nov. 17, averting a partial shutdown but not imposing any of the spending cuts or changes to border security that his hardline colleagues had called for.

The bill, which was approved by the Senate on a broad bipartisan basis and signed into law by Biden, is meant to give lawmakers more time to agree on a deal to fund the government through Sept. 30, 2024.

An ouster of the speaker would complicate that process.

"It is destructive to the country to put forth this motion to vacate," Representative Mike Lawler, a Republican, said on ABC. "By putting this motion to vacate on the floor, you know what Matt Gaetz is going to do? He is going to delay the ability to complete that work over the next 45 days."

Gaetz had been threatening to move against McCarthy for weeks.

Republican Representative Byron Donalds, a member of the hardline House Freedom Caucus who had been nominated to challenge McCarthy for speaker in January, declined to say how he would vote.

"I don't know right now," Donalds said in an interview on Fox. "I gotta really think about that because there's a lot of stuff going on."

'GO AHEAD AND TRY'

McCarthy decided to bring a vote on a measure that could win Democratic support, knowing full well that it could jeopardize his job. One of his advisers told Reuters the speaker believed some hardliners would try to oust him under any circumstances.

"Go ahead and try," McCarthy said in comments directed at his opponents on Saturday. "You know what? If I have to risk my job for standing up for the American public, I will do that."

The bipartisan measure succeeded a day after Republican Representative Andy Biggs, a leading hardliner, and 20 others blocked a Republican stopgap bill that contained sharp spending cuts and immigration and border restrictions, all of which hardliners favor.

The bill's failure ended Republican hopes of moving a conservative measure and opened the door to the bipartisan measure that was backed by 209 House Democrats and 126 Republicans. Ninety Republicans opposed the stopgap.

Hardliners complained that the measure, known as a continuing resolution, or CR, left in place policies favored by Democrats including Biden, Senate Majority Leader Chuck Schumer and former House Speaker Nancy Pelosi.

DEMOCRATIC RESPONSE UNCLEAR

It was not clear what action Democrats might take if a Republican moved to vacate the chair and the House voted on the measure.

Some Democrats have suggested they could support McCarthy if an ouster attempt occurred at a turbulent time. Others have suggested they could back a moderate Republican willing to share the gavel with them and allow power sharing within House committees. Others have shown no interest in helping any speaker candidate aside from House Democratic leader Hakeem Jeffries.

U.S. Representative Alexandra Ocasio-Cortez, a leading progressive Democrat, said her party was unlikely to help McCarthy keep his job without receiving concessions from Republicans.

"I don't think we give up votes for free," Ocasio-Cortez told CNN's State of the Union.

Asked if she would vote on a measure to oust McCarthy, Ocasio-Cortez said: "Would I cast that vote? Absolutely. Absolutely. I think Kevin McCarthy is a very weak Speaker. He clearly has lost control of his caucus."

(Reporting by David Morgan, additional reporting by Jason Lange and Leah Douglas; Editing by Scott Malone, Lisa Shumaker and Grant McCool)