House Ways and Means Committee Chairman Richard Neal, D-Mass., has subpoenaed the Treasury Department and the IRS to follow up on his request for President Trump’s tax returns.

"While I do not take this step lightly, I believe this action gives us the best opportunity to succeed and obtain the requested material," Neal said in a statement. "I sincerely hope that the Treasury Department will furnish the requested material in the next week so the committee can quickly begin its work.”

Neal said that he issued subpoenas to Treasury Secretary Steven Mnuchin and IRS Commissioner Charles Rettig for six years of Trump's personal and business tax returns.

Other House committees have already subpoenaed Trump’s banks and accountant to obtain his financial records. The president is challenging the merits of those subpoenas in court, arguing that Congress is going past its constitutional power to obtain his financial information.

Treasury has made a similar argument in its rebuff of Neal’s request for Trump’s tax information.

Neal himself seemed to doubt the effectiveness of subpoenas in remarks made to reporters earlier this week.

"They seem not to be paying a lot of attention to these subpoenas," said Neal on Tuesday, referring to subpoenas issued by other House committees.

On Friday, Rep. Kevin Brady, R-Texas, echoed Trump's argument against cooperating with congressional requests for his financial information in a letter to Neal requesting that he end the investigation into Trump’s tax returns.

“[F]rom press accounts to statements by senior members of this Committee, it has become obvious that your supposed legislative purpose is just a pretext, and your request is merely a means to access and make public the tax returns of a single individual for purely political purposes,” wrote Brady.

Legal experts with experience in congressional investigations and constitutional law say that the administration has a tough legal battle ahead, but that Trump could be successful in delaying access to documents until after the 2020 presidential election.