Officials from the justice department and FBI have begun consulting lawyers amid fears that they will be prosecuted when Donald Trump returns to the White House, it has been reported.

The concerns have been driven by Trump’s vows to seek “retribution” against members of a “deep state” that he claims deliberately set out to undermine him when he was president and falsely alleges was weaponised against him after he left office.

They have been intensified by the president-elect’s nomination of the rightwing former Florida congressman Matt Gaetz as attorney general, a position that would put him in charge of the DoJ and America’s federal law enforcement agencies.

Gaetz – who himself underwent a two-year FBI investigation into sex trafficking allegations that ended without charges – was chosen after reportedly telling Trump that he would “go over there and start cuttin’ fuckin’ heads”. He had previously called for “a full-court press against this WEAPONIZED government” in a social media post.

“If that means abolishing every one of the three letter agencies, from the FBI to the ATF [Bureau of Alcohol, Tobacco, Firearms and Explosives] I’m ready to get going!” he continued.

The threats had prompted serving and retired officials to contact defence lawyers even though they are convinced they have committed no crime, NBC reported.

Several DoJ officials wept following Trump’s resounding election victory over Kamala Harris, according to the network, upset that many Americans believed his narrative that the department had been corrupted and weaponised to conduct a political witch hunt against him.

“Everything we did was above board,” said a former senior FBI official who had begun taking legal advice because of fear of prosecution. “But this is a different world.”

A former senior justice department official who served during Trump’s first presidency said the choice of Gaetz was a mark of the incoming president’s seriousness about seeking payback against those he believed had wronged him.

“He needs to be able to control the department, which he can do through a loyal [attorney general] beholden to him,” the former official said. “[Gaetz] understands that he owes everything to Trump, who can protect Gaetz as well through his pardon power. Trump is confident that Gaetz will do whatever Trump tells him to do.”

Trump bears a grudge against the justice department after it pressed charges relating to his attempts to overturn the 2020 presidential election, which he falsely claimed was stolen. It also investigated his improper retention of classified documents from his presidency, which he kept in his Mar-a-Lago home.

Charges from both investigations were rolled into an inquiry conducted by the special prosecutor, Jack Smith, who was appointed by the current attorney general, Merrick Garland.

Trump has repeatedly assailed Smith and during the election campaign called for him to be thrown out of the country.

The president-elect also continues to be angry about allegations that he colluded with Russia to interfere in the 2016 election, which resulted in an investigation by another special prosecutor, Robert Mueller.

Allies of Trump have suggested that Smith in particular could be investigated under a charge he levelled against Trump: conspiracy against rights.

Ilya Somin, a law professor at George Mason University, told NBC that there was little scope for prosecuting Smith under such a charge. However, he said prosecutors could investigate individuals over a long period and find minor crimes unrelated to the original charges.

“If you think about it, a majority of adult Americans have probably violated federal laws, such as smoking marijuana, at some point in their lives,” he said.

During the campaign, Trump repeatedly said the choice of attorney general would be his most important cabinet appointment.

Observers say his goal is to assert control over the justice department, which has been conventionally viewed as politically independent from White House interference since Watergate.

Stephen Gillers, an ethics professor at New York University law school, said Trump’s objective is to end that independence.

“Trump aims to neutralize sources of power that may impede him,” he told NBC. “That includes the law and legal institutions. He will tolerate no interference when the department’s decisions will benefit Trump and his buddies or when its power can be deployed to retaliate against his enemies.”