WASHINGTON — An organization representing career Internal Revenue Service employees has joined a lawsuit over the contentious settlement reached in connection with President Donald Trump’s lawsuit against the IRS, challenging a carveout that would give him and members of his family immunity from certain tax audits.

A Jan. 6 prosecutor fired by the Trump administration and others previously sued to block a fund that could have gone to Trump allies who said they were victims of weaponization, potentially including Jan. 6 rioters. A federal judge then temporarily blocked the fund from moving forward in May.

Now, an amended version of lawsuit filed in the Eastern District of Virginia on Thursday afternoon alleges that the IRS audit immunity that Acting Attorney General Todd Blanche agreed to for Trump and his family members in connection with the purported settlement is unlawful and unconstitutional. The National Treasury Employees Union (NTEU), which represents career IRS auditors, has joined the litigation.

The order would provide the president “and his relatives and affiliates with a lucrative benefit not available to any other Americans,” the lawsuit argued.

The lawsuit describes the purported settlement as “an unprecedented, unlawful, and breathtakingly corrupt attempt by the President and members of his cabinet to manipulate the legal process and laws intended to prevent political interference to achieve benefits that President Trump and his political allies could not have obtained lawfully.”

Both the Trump tax carveout and the $1.776 billion “Anti-Weaponization Fund” grew out of a lawsuit Trump and his family members filed against the government he controls over the disclosure of his tax returns by a former IRS contractor, who was imprisoned over the disclosure.

Skye Perryman, the president and CEO of the group Democracy Forward, which brought the initial case, said Thursday they were “honored to represent brave IRS employees in this first of its kind case challenging the unlawful scheme, while we continue to pursue the challenge to the $1.776 billion slush fund that will line the pockets of violent criminals, including those who perpetrated the attacks on the Capitol and our elections on January 6.”

Blanche, Perryman said, “cannot tell the public the slush fund is dead while preserving every legal mechanism necessary to resurrect it at a moment’s notice.”

Two key Republican senators — Thom Tillis of North Carolina and John Cornyn of Texas — had raised issues with the “Anti-Weaponization Fund,” but then reached a deal with Blanche to memorialize the end of the fund.

Blanche’s nomination to take over the top Justice Department role is now pending before the full Senate after he was voted out of the Senate Judiciary Committee this week.

The Justice Department could still pay out Jan. 6 rioters even without the fund, although this week the Justice Department told a federal judge in Florida to toss a lawsuit filed on behalf of a number of Jan. 6 participants, saying their claims were barred by the statue of limitations.

The Justice Department did not immediately respond to a request for comment on the amended lawsuit.