House Democrats sue Trump administration for president's tax returns

House Democrats on Tuesday filed a lawsuit against the Trump administration seeking six years of President Donald Trump's tax returns, escalating their standoff with the Trump administration for the president's financial records and sending the issue to federal court.

House lawyers, representing the Ways and Means Committee, are challenging the administration's refusal to comply with a subpoena for the records, and specifically named the Treasury Department, Internal Revenue Service, Treasury Secretary Steven Mnuchin and IRS Commissioner Charles Rettig in the suit.

"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 complaint reads.

Jay Sekulow, the president's lawyer said in a statement, "We will respond to this latest effort at Presidential harassment in Court."

Late Tuesday, Steven Groves, deputy White House press secretary, said, "While the crisis at our southern border worsens, Democrats continue to focus their efforts on Presidential harassment."

Groves added that the chairman'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," he said. "The only thing more political than the Committee's crusade for the President's tax returns is its sham lawsuit."

While congressional aides and legal experts expect the lawsuit to unfold over several months -- and possibly into next year -- the outcome could have implications in the larger struggle between House Democrats and the Trump administration over the president's financial information, and documents, information and testimony in their broader oversight inquiries.

Democrats made the request under a 1920s-era provision of the U.S. tax code, which states that the IRS secretary "shall furnish" any individual's tax returns to the leaders of three congressional committees upon request.

"Despite its mandatory obligation, the Treasury Department failed to comply with the law and denied the Committee's request. The Administration also refused to comply with the subpoenas I subsequently issued in an effort to obtain the materials. Due to that noncompliance, the Committee is now pursuing this matter in the federal courts," Chairman Richard Neal said in a statement Tuesday.

Republicans have accused Democrats of weaponizing the tax code to target the president, and that the effort serves no legislative purpose.

"The Democrats' partisan, flawed lawsuit continues their unprecedented and illegitimate pursuit to expose President Trump's private tax information," Rep. Kevin Brady, R-Texas, the top Republican on the tax-writing committee. "This not only weaponizes the tax code and puts every taxpayer at risk, this lawsuit goes further and - for the first time - circumvents America's democratic process by replacing the U.S. House's voice with Nancy Pelosi's voice."

Brady said he would introduce a resolution condemning Democrats' effort.

Democrats' full complaint is available here:

ABC News' Meridith McGraw contributed to this report.