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The Democrat-led House Ways and Means Committee filed a lawsuit on Tuesday to enforce subpoenas and obtain President Donald Trump’s tax returns, an escalation in a fight for the President’s personal financial information.

The lawsuit was filed in D.C. District Court against Treasury and the IRS and their respective leaders, Steve Mnuchin and Charles Rettig.

House Ways and Means Chairman Richard Neal is seeking the President’s tax returns using a little-known IRS provision known as 6103, which allows the Chairmen of the House Ways and Means Committee and the Senate Finance Committee to request and obtain an individual’s tax information for a legitimate legislative purpose.

The move comes months after Neal made his initial request for the President’s tax information and as outside groups and other liberals on the Ways and Means Committee grew impatient with the pace of Neal’s efforts. Neal initially made his request for Trump’s tax returns on April 3. After a series of follow-up letters, the Treasury Department formally denied the request at the beginning of May, and Neal issued subpoenas to the IRS and Treasury Department on May 10.

“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,” House attorneys wrote in the complaint.

Jay Sekulow, counsel to the President, responded to the suit Tuesday afternoon by saying in a statement, “We will respond to this latest effort at Presidential harassment in Court.”

The complaint states that the “refusal to produce the requested materials” has deprived the House panel of “information necessary to complete its time-limited investigation,” and goes on to say that the committee is asking the court to order the defendants “to comply with Section 6103(f) and the subpoenas by producing the requested information immediately.”

The complaint argues that the committee is not required to justify its reasons for seeking tax returns under Section 6103, but states that the panel “is 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.”

According to the suit, a bipartisan group of committee staff members met with Treasury and IRS officials on June 10 in order to learn more about the presidential audit program.

However, none of the officials from Treasury or IRS at the meeting had ever worked on the Presidential audit program, the lawsuit states, adding staff committee members left the meeting with more questions than answers.

The committee, at the request of the Treasury department, sent Treasury and the IRS 300 questions after the meeting about the presidential audit program, “the vast majority of which had not been answered in the meeting,” the complaint states.

The top Republican on the Ways and Means committee, Rep. Kevin Brady of Texas, reacted to the lawsuit on Tuesday by saying he will introduce a resolution opposing the move.

“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.”

Democrats had argued that under 6103 authority, Neal did not need to issue a subpoena, but internal deliberations with House Counsel got Neal to the point where the advice was that a subpoena could bolster the case in court. The Democrats on Neal’s committee have argued that they need access to the President’s tax returns in order to understand how the IRS administers the presidential audit program. Meanwhile, the Treasury Department has argued it is not a legitimate legislative purpose.

The lawsuit piles onto several other court fights involving other committees and members of Congress seeking Trump financial records.

In two other court cases, Trump has tried to stop the House Oversight Committee, the House Intelligence Committee and the House Financial Services Committee from getting his financial records from Capital One bank, Deutsche Bank and the accounting firm Mazars USA.

So far, trial-level judges have sided firmly with Congress, saying the committees have broad authority to pursue investigations with subpoenas like these. Trump is appealing both court decisions, and the cases aren’t likely to be resolved until at least next month.

“There can be no doubt as to the power of Congress, by itself or through its committees, to investigate matters,” federal Judge Edgardo Ramos said at a court hearing in May. “Without the power to investigate … Congress could be seriously handicapped in its efforts to exercise its constitutional function wisely and effectively.”

This story has been updated with additional developments Tuesday.

CNN’s Pamela Brown contributed to this report.