Massachusetts Rep. Richard Neal says his request this week for President Trump’s tax returns is about policy, not politics. Nevertheless, he is gearing up for a battle in court.

The chair of the House Ways and Means Committee Wednesday formally requested the last six years of Trump’s tax returns in a letter to the IRS commissioner. It was the first request for a sitting president’s tax returns in 45 years.

"We have resisted politics," he said, in an interview Friday with WGBY, WGBH’s partner station in Springfield, Mass. "We did not link this to the Mueller report. We did not link this to some nefarious undertaking. Instead I think we took a very measured position, as I insisted that we would, from day one."

While many Democrats have lauded the move, many Republicans have criticized Neal’s request. Rep. Kevin Brady of Texas, the senior Republican on the Ways and Means panel, denounced the move as "an abuse of the tax-writing committees' statutory authority."

Iowa Sen. Chuck Grassley, another Republican, said, "It's Nixonian to the core."

“When you strip away all of their pretext, and when you strip out their circular logic, all you have are Democrats who want to go after the president any way they can,” Grassley said. “They dislike him with a passion, and they want his tax returns to destroy him.”

Neal rejected that premise, stating that the intent behind the request was not to destroy Trump. Rather, he said, the committee’s intention was to test Section 6103 of the U.S. tax code, which Neal argues gives the Ways and Means Committee authority to obtain tax returns upon request.

“This was not motivated by malevolence,” he said. “Our intent is to test a federal law that has been on the books since 1924 and to apply the full tenor of that law to the request that we've made and to make sure that that law under again the magnifying glass stands up.”

Trump has said he “would not be inclined” to give Congress his tax returns. Since he campaigned for the presidency, he has dismissed calls to release the documents, saying he is under audit. The IRS declined to comment on Neal’s request, but agency officials have said in the past that being under audit doesn’t prohibit anyone from releasing their returns.

Neal's request is expected to prompt a protracted legal battle between Congress and the White House that could take years to resolve.

Whether the courts will agree with Neal’s interpretation of this law is uncertain, and the White House appears to be building a case to fight it. Neal said his committee is also “in the midst of building a case,” and he said he assumes this will “head to court in the not too distant future.”

Neal said it was also important to request Trump’s tax returns to exercise Congress’ oversight role.

“Oversight responsibility for legislative function dates at least to Magna Carta. It is part of the Jeffersonian notion of how the legislative branch might oversee the executive branch,” Neal said. “Congress is mentioned as the first branch of government for that very purpose.”

Neal said he hopes Trump will voluntarily comply with the committee’s request, and he has given the IRS commissioner a deadline of Apr. 10 to respond. He said the committee has a strategy for next steps should he not receive a response by the deadline but declined to share what that strategy is.

The Associated Press contributed to this report.

This post has been updated.