The House Ways and Means Committee filed a lawsuit Tuesday in U.S. District Court in Washington, D.C., against Treasury Secretary Steven Mnuchin and IRS Commissioner Charles Rettig demanding access to President Trump's tax returns.

House Democrats, who in November regained the chamber for the first time in eight years, had engaged in a months-long battle to obtain Trump's tax statements from 2013 to 2018 with no compliance from the administration.  

House Ways and Means Chairman Richard Neal, D-Mass., asked for the returns on April 3, with the Treasury Department denying the request. This resulted in Neal using subpoenas on May 10 to try and obtain the information from the IRS and the Treasury Department.   

Rep. Neal told CNN in November that he hoped Trump would voluntarily release his returns but expected a legal battle.

Mnuchin has argued that such subpoena requests "lack a legislative purpose" and that they are unreasonable. 

The request issued by Neal in April is called a 6103 (f) request, which allows certain members of Congress to get access to tax return information of an American. 

"In refusing to comply with this statute, Defendents have mounted an extraordinary attack on the authority of Congress to obtain information needed to conduct oversight of the Treasury, the IRS, and the tax laws on behalf of the American people who participate in the nation's voluntary tax system," the legal complaint reads.

"We are here today because Donald Trump and his enablers have sneered at our laws and avoided the thinnest accountability for their corruption," said Bill Pascrell, D-N.J., in a statement. "The Ways and Means Committee must file this action to stand for rule of law."

Trump's tax returns have been a major controversy during his administration as some fear that he has paid very little, despite his self-proclaimed net worth of billions of dollars. Marches took place on April 15, 2017, demanding Trump release his tax returns. 

Legal experts told Reuters that the court battle could extend well into the 2020 presidential election season. 

"I expect that Trump will stall at every opportunity," said Steven Rosenthal, a tax lawyer at the Urban-Brookings Tax Policy Center in Washington, D.C.

"Delay is a victory for Trump," he added.