Failing to obtain President Trump’s tax returns via request or subpoena, the Democrat-led House Ways and Means Committee is now suing for them.

In a lawsuit filed Tuesday, the committee claimed the Trump administration was violating federal law by refusing to comply with its demands. A statute allows the committee to request an individual’s tax return information, but Treasury Secretary Steve Mnuchin shot down the request.

“In refusing to comply with the statute, Defendants have mounted an extraordinary attack on the authority of Congress to obtain information needed to conduct oversight of Treasury, the IRS, and the tax laws on behalf of the American people who participate in the Nation’s voluntary tax system,” the lawsuit said.

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The White House fought back, with an administration source telling Fox News that “the Justice Department will litigate this, but yes it will be challenged.”

Deputy Press Secretary Steven Groves said: “While the crisis at our southern border worsens, Democrats continue to focus their efforts on Presidential harassment. Chairman [Richard] Neal’s willingness to use his powerful Committee to go after his political opponents is a danger to democracy. The Committee has no legitimate legislative purpose for which it can demand the President’s tax returns, and it is evident that they are only interested in partisan games. The only thing more political than the Committee’s crusade for the President’s tax returns is its sham lawsuit.”

The committee claimed the law gave it “unfettered access to tax return information,” but Mnuchin had claimed the panel lacked a legitimate legislative purpose, which the Supreme Court said was necessary to make such inquiries. The committee claimed the law did not permit the Treasury Department to refuse and did not require any such legislative purpose.

Mnuchin was named as a defendant in the case, as was IRS Commissioner Charles Rettig, as well as the IRS and Treasury Department. The IRS and Treasury Department did not immediately respond to Fox News' requests for comment.

University of Iowa Law Professor Andy Grewal, who has written on the subject, said Tuesday he predicted the House committee may find early success in the lawsuit, but that the Supreme Court ultimately would rule that it did not have the power to bring the lawsuit.

“I would not be surprised if a district court orders the Treasury to turn over the returns,” Grewal tweeted. “But my prediction is that in this lawsuit or another, the Supreme Court says that the legislature lacks standing to sue the executive branch (ie, the case gets tossed out).”

In a separate comment to Fox News, Grewal warned of the precedent the lawsuit could set if it's successful.

"The committee has asserted an extraordinarily broad understanding of its own powers, saying that no one -- not the executive branch, not even the Supreme Court -- can question its motives," he said. "Acceptance of that position would mean that Congress could issue subpoenas even when motivated by racism and bigotry. Courts may be hesitant to accept such a broad construction of the House's investigatory power."

Despite claiming that it did not require any legislative purpose, the committee did claim it had one. The complaint alleged that the panel needed Trump’s tax return information because it was “investigating the IRS’s administration of various tax laws and policies relating to Presidential tax returns and tax law compliance by President Trump, including whether the IRS’s self-imposed policy of annually auditing the returns of sitting Presidents is working properly[.]”

Trump has said in the past that the reason he did not release his tax returns during the 2016 campaign, per tradition, was because he was under audit. The lawsuit cited a similar comment by Trump in April 2019, where he said he would not give Congress his tax returns while under audit.

The lawsuit also claimed the committee urgently needed the president's tax return information because of the consideration of tax legislation that "would govern the next Presidential election," including bills that would require candidates in 2020 to disclose their tax returns.

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Committee member Rep. Bill Pascrell Jr., D-N.J., claimed that the lawsuit was a necessary measure due to the administration’s refusal to comply.

“Litigation is always a last resort. We are here today because Donald Trump and his enablers have sneered at our laws and avoided the thinnest accountability for their corruption. The Ways and Means Committee must file this action to stand for rule of law,” he said in a statement. “Despite Republicans’ efforts to cover-up, Americans cry out for oversight and voted in a new House to enforce that demand in November.”

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Republicans on the committee, meanwhile, have been looking to take their own action. Top GOP member Rep. Kevin Brady, R-Texas, said after the lawsuit was filed that he was introducing a resolution against it.

“The Democrats’ partisan, flawed lawsuit continues their unprecedented and illegitimate pursuit to expose President Trump’s private tax information,” Brady said in a statement. “This is a dangerous course of action. For this reason, I am introducing a resolution to preserve the integrity of the People’s House from the attacks of the elite few and restore the voice of every American.”

Fox News' Kristina Biddle and Edward Lawrence contributed to this report.