Donald Trump announced firebrand ex-lawmaker Matt Gaetz as his pick for attorney general Wednesday, naming a fierce defender who would be well-placed to make good on the president-elect's threats of revenge against political foes.

"Few issues in America are more important than ending the partisan Weaponization of our Justice System," Trump posted on social media. "Matt will end Weaponized Government... and restore Americans' badly-shattered Faith and Confidence in the Justice Department."

Gaetz, a Floridian and a US congressman since 2017, is among Trump's most controversial nominations as he looks to fill out his cabinet after victory against Democrat Kamala Harris in last week's presidential election.

Gaetz resigned from his seat in the House of Representatives hours after Trump's bombshell announcement on Wednesday.

Trump has called for retribution against many perceived political foes whom he baselessly accuses of wielding the might of the Justice Department against him in politically motivated prosecutions.

Democrats fear that Gaetz, 42, will help him weaponize the department to launch exactly those types of "show trial" prosecutions.

As attorney general, Gaetz would drive all aspects of the work of the Justice Department, which for years has carried out an investigation into sex trafficking and obstruction of justice allegations involving him.

Gaetz, who denies all wrongdoing, was told last year that there would be no charges against him, but he remains the subject of a House ethics investigation.

Police began looking at Gaetz as they were investigating his friend, former tax collector Joel Greenberg, who was sentenced in 2022 to a prison term of 11 years after admitting to sex trafficking a minor and other charges.

In September, Gaetz said in a statement he would no longer help congressional investigators, accusing them of leading a "political payback exercise" and calling the probe "uncomfortably nosy."

Republican and Democratic senators immediately voiced doubts that Gaetz's nomination would survive the confirmation process, which can involve intense questioning during difficult, fraught hearings.

Gaetz will likely only be able to lose three Republicans and still get the green light from the Senate.

CNN, citing unnamed sources reported that House Republicans were meeting behind closed doors when news of Gaetz's nomination emerged -- prompting "an audible gasp from the members in the room."

Republican Iowa Senator Joni Ernst said Gaetz would have "his work cut out for him," according to Scripps News, which also reported that the party's Alaska Senator Lisa Murkowski said: "Do you think he's a serious candidate? Not as far as I'm concerned."

A third senator from the party's political middle, Susan Collins, told reporters she was "shocked" by the announcement.

"That shows why the advice and consent process is so important, and I'm sure that there will be a lot of questions raised at his hearing."

Other Trump nominations

Director of National Intelligence: Tulsi Gabbard

Gabbard, a former Hawaii congresswoman, switched sides from the Democrats to back Trump's reelection. She has long held isolationist foreign policy views and made comments supportive of US adversaries, including Putin's Russia.

As director of national intelligence, she would oversee coordination of the 18 intelligence agencies.

Homeland Security Secretary: Kristi Noem

A longtime Trump loyalist and South Dakota governor, Noem would play a key role in any Trump effort to restrict immigration and deport undocumented migrants.

Noem became famous for admitting that she shot an "untrainable" pet dog, saying this showed her ability to make tough choices.

Veteran immigration official Tom Homan is set to be the country's "border czar."

UN ambassador: Elise Stefanik

New York congresswoman Stefanik is a vocal Trump ally and pro-Israel stalwart.

Ambassador to Israel: Mike Huckabee

Trump says the former Arkansas governor, a Christian pastor-turned-politician, "loves Israel, and the people of Israel, and likewise, the people of Israel love him."

© Agence France-Presse