WASHINGTON — The former chief of the IRS’s criminal division said Tuesday that he was “not aware” of an instance like the tax agency’s removal of the investigative team in charge of first son Hunter Biden’s case.

John Fort, who worked at the IRS from 1991 to 2020, said the reported retaliation against the whistleblower who contacted Congress to allege a coverup in the case was a “serious allegation.”

“In your time in the IRS in the investigatory division or criminal division, was there ever another instance where an entire IRS investigatory team was pulled off a tax case?” Sen. Ron Johnson (R-Wis.) asked at a Senate Finance Committee hearing.

“I’ve spent 30 — almost 30 years with IRS criminal investigation. I’m not aware of a situation such as that,” Fort replied. “But again, when I retired from the organization at the end of 2020, I was in charge of about 3,000 people, including 2,100 agents, so I can’t say with certainty whether or not that happened.”

Johnson pressed: “The fact that the Justice Department has removed the entire investigatory team off of the case, that just smacks of partisanship and erodes the American people’s confidence that the IRS will be fair and impartial and administer the tax code equally.

“Do you agree that that erodes confidence in the IRS — this recent revelation?” Johnson asked Fort, who now works in private practice.

“Federal law prohibits me from discussing any specific taxpayer at all, but I would just agree that it’s a serious allegation,” the former IRS chief investigator said.

“Well, again,” Johnson continued, “having an entire IRS investigatory team pulled off any case would certainly get you scratching your head, right? Highly concerned about what’s pulling off here?”

“In my experience, you know, I’m not personally aware of a situation such as that,” Fort said.

Johnson said the Democrat-led hearing’s focus on boosting federal resources to catch “wealthy tax cheats” was ironic given that President Biden’s son appeared to be shielded in the five-year-old investigation.

The IRS whistleblower supervised the Hunter Biden investigation since early 2020 and contacted Congress last month to allege a cover-up. He already made internal complaints to the Treasury and Justice Department inspectors general.

The informant has not yet set a date with congressional leaders for depositions after alleging “preferential treatment” and false testimony to Congress about the probe but is expected to do so soon.

The whistleblower’s legal team alerted Congress on Monday to the alleged retaliation.

“Today the Internal Revenue Service (IRS) Criminal Supervisory Special Agent we represent was informed that he and his entire investigative team are being removed from the ongoing and sensitive investigation of the high-profile, controversial subject about which our client sought to make whistleblower disclosures to Congress,” attorneys Mark Lytle and Tristan Leavitt wrote.

“He was informed the change was at the request of the Department of Justice.”

The Republican-led House Oversight Committee tweeted Tuesday, “This whistleblower is alleging the Biden [administration] is blocking efforts to charge Hunter Biden for federal violations. Congress must thoroughly investigate this alleged retaliation and hold accountable those who are covering up any crimes committed by the President’s son.”

House Speaker Kevin McCarthy (R-Calif.) tweeted, “The repeated weaponization of the federal government to attack one political party and protect the other is un-American. [The House Ways and Means Committee] will expose any possible cover-up at the IRS, and Republicans will protect the whistleblowers who shine a light on government misconduct.”

IRS Commissioner Daniel Werfel said at a House hearing last month that “there will be no retaliation for anyone making an allegation or a call to a whistleblower hotline” — but the whistleblower’s lawyers wrote Monday that “this move is clearly retaliatory and may also constitute obstruction of a congressional inquiry.”

The Justice Department didn’t respond to The Post’s request for comment and the IRS released a statement saying only that it stands by Werfel’s remarks about protecting whistleblowers.

“Under federal law, the IRS can’t comment on specific taxpayer matters. In general, the IRS is deeply committed to protecting the role of whistleblowers, and there are robust processes and procedures in place to protect whistleblowers,” the agency said.

“As IRS Commissioner Danny Werfel has stated, we will not tolerate retaliation against any IRS employee making a whistleblower allegation. When suggestions of wrongdoing are raised, we work with all appropriate parties, including the Treasury Inspector General for Tax Administration, to ensure the integrity of the whistleblower process is safeguarded.”

Exactly one week after the whistleblower first contacted Congress on April 19, Hunter Biden’s legal team met with Justice Department leaders.

It’s unclear if the first son was offered a plea deal at the meeting, which was widely seen as a sign that prosecutors reached the final stages of the investigation led by Delaware US Attorney David Weiss, a Trump administration holdover recommended to his post by the state’s two Democratic senators.

If the 53-year-old first son ultimately is indicted, the removal of the investigative team could hamstring a complex prosecution.

Hunter Biden allegedly failed to pay taxes on millions in largely foreign-sourced income.

Joe Biden as vice president was involved in many of his international business relationships — meeting with Hunter’s clients and associates from China, Mexico, Kazakhstan, Russia, and Ukraine — and the House Oversight Committee last week described nine Biden family members who allegedly got foreign income.

The IRS whistleblower has not publicly confirmed that his complaint pertains to Hunter Biden, but congressional sources have done so.

The Post previously reported that Attorney General Merrick Garland’s testimony to Congress is being contested by the IRS worker. Garland repeatedly said that Weiss had unilateral authority to make charging decisions, even if crimes occurred outside Delaware.

A different whistleblower informed Sen. Chuck Grassley (R-Iowa) this month that the FBI has an informant file from 2020 alleging that Joe Biden accepted bribes while vice president.

House Oversight Committee Chairman James Comer (R-Ky.) issued a subpoena for the file, but last week the FBI refused to give the document to Congress.

Hunter, whose “sugar brother” Kevin Morris supplied about $2 million last year to settle his overdue tax bill, wrote in emails retrieved from his abandoned laptop that he shared up to “half” of his income with his father, though the president reportedly is not a target of the Weiss-led investigation.

In addition to alleged tax fraud, the criminal probe reportedly has reviewed whether the first son laundered money, violated the Foreign Agents Registration Act, and lied about his drug use on a gun purchase form.