A far-right Republican lawmaker has filed a motion to oust US Speaker Kevin McCarthy from his post, after he brokered a budget deal with Democrats to avoid a government shutdown.

Florida legislator Matt Gaetz, a long-time McCarthy critic and Donald Trump supporter, accused fellow Republican McCarthy of "working at the pleasure of the Democrats."

What prompted the motion?

Gaetz had threatened to use the "motion to vacate" against McCarthy before. But his decision to deliver on the threats was prompted by the weekend's budget deal, which McCarthy reached with the Democrats, preventing a government shutdown.

Many conservatives within the Republican Party's lawmakers had rejected the budget deal. They refused fresh federal funding without deep spending cuts, as well as opposing additional US support to Ukraine.

Gaetz acknowledged that the motion was unlikely to work. He nevertheless said: "If the Democrats want to own Kevin McCarthy, they can have him. Because one thing I'm at peace with is, when we stand here a week from now, I won't own Kevin McCarthy anymore."

"Bring it on, let's get over it," was McCarthy's response in comments during a TV interview with CBS.

How would the motion play out?

Gaetz's rare motion has only been used twice against Republican speakers in the past century. If it works, McCarthy will be the first US speaker to be ousted.

In an effort to appease fellow Republicans back in January, McCarthy introduced amendments, including one which allowed for the motion to be triggered by a single lawmaker. McCarthy was then able to secure the speaker post, on the 15th vote.

The House should next schedule a vote on the motion within two legislative days. It is unclear whether McCarthy will need to rely on Democrats' votes to protect him against an ouster.

The move comes as tension grows within the Republican Party, especially with a divide over Donald Trump's presidential bid.

Democrat lawmaker Gregory Meeks described it as "another day at the show."

rmt/ (AFP, AP)