Hunter Biden has filed a lawsuit in a Washington, D.C., federal court against the Internal Revenue Service over alleged "unlawful disclosures" made by a pair of whistleblowers who accused government prosecutors of mishandling their investigation into the president's son -- a claim the Justice Department has denied but nonetheless breathed fresh life into Hunter Biden's legal tribulations.

Attorneys for Biden, 53, accused Gary Shapley and Joseph Ziegler, both veteran IRS investigators, of waging a campaign to "to embarrass and inflict harm on Mr. Biden" by improperly sharing his private taxpayer information in media interviews.

"During these interviews, Mr. Shapley and Mr. Ziegler provide unsubstantiated and selectively chosen allegations of nefarious and potentially criminal behavior," wrote Hunter Biden's attorney, Abbe Lowell.

The IRS "failed to take reasonable steps to prevent its personnel from unlawfully disclosing" Hunter Biden's confidential taxpayer information in violation of the Privacy Act, Lowell argued.

After a nearly five-year probe, Hunter Biden was indicted last week on felony gun charges, two months after a plea deal he had negotiated with prosecutors fell apart under questioning from a federal judge.

Those developments happened in the wake of troubling claims made by Shapley and Ziegler, who approached Congress in April with allegations that senior Justice Department officials blocked efforts to bring more serious charges against Hunter Biden, limited their investigative scope, and refused to grant special counsel status to the Trump-appointed U.S. attorney who oversaw the case.

The Justice Department and Attorney General Merrick Garland have denied those claims, defending U.S. Attorney David Weiss' independence over the matter. Weiss himself wrote lawmakers in June to clarify that he had "full authority" to bring charges whenever and wherever he chose.

But those denials have done little to blunt concerns that the Justice Department offered the younger Biden a "sweetheart deal" from prosecutors, as congressional Republicans have claimed. Nearly half of Americans said they were not confident that the Justice Department has handled its probe of Hunter Biden in a fair and nonpartisan manner, according to an ABC News/Ipsos poll from earlier this month.

In a statement responding to the lawsuit, attorneys for Shapley said, "Neither IRS SSA Gary Shapley nor his attorneys have ever released any confidential taxpayer information except through whistleblower disclosures authorized by statute. Once Congress released that testimony, like every American citizen, he has a right to discuss that public information."

IRS officials declined to comment on the suit.

In the course of their "media circus," as Lowell framed it, Shapley and Ziegler made statements that fell "well outside the bounds of the whistleblower protections."

Congressional Republicans voted in June to release the transcripts of interviews they'd conducted with the two whistleblowers. But in subsequent television and podcast interviews, the whistleblowers made statements not included in their testimony, Lowell wrote -- despite instruction from the committee not to share what was discussed in the interview "to individuals not designated to receive such information."

As a result, according to the lawsuit, the IRS shirked its responsibility to protect Hunter Biden's tax information from being made public.

"The IRS has never instructed Mr. Shapley, Mr. Ziegler, or their representatives to refrain from publicly and unlawfully disclosing Mr. Biden's confidential tax return information, much less taken reasonable steps to prevent its personnel from unlawfully accessing and disclosing Mr. Biden's tax return information," Lowell wrote.

Attorneys for Hunter Biden are seeking $1,000 in damages for each "unauthorized disclosure" of his tax information, a declaration that the IRS "willfully, knowingly, and/or by gross negligence, unlawfully disclosed Mr. Biden's confidential tax return information," and any documents in the IRS' possession related to Hunter Biden's tax information.