New York Gov. Andrew Cuomo recently signed into law legislation designed to make it easier for Congress to obtain President Donald Trump's state tax returns.

So far, the only Democrat able to use the law wants nothing to do with it.

It's just one of a series of decisions that have landed House Ways and Means Chairman Richard Neal, D-Mass., in hot water with those on the left who feel the longtime lawmaker hasn't done nearly enough to obtain the president's tax returns.

In a sign of progressives' anger, a Democrat on Monday announced that he will take on Neal, a moderate who has been in office since 1989, in a primary.

"There's an urgency to this moment in Massachusetts' 1st District and our country, and that urgency is not matched by our current representative in Congress," Holyoke, Massachusetts, Mayor Alex Morse said in a video announcing his candidacy. "We need new leadership that understands that we can no longer settle for small, incremental and compromising progress. We need to be on offense."

The progressive magazine The American Prospect also has repeatedly taken issue with Neal's leadership, saying his committee "has shown none of the zeal for oversight exhibited by its counterparts."

After the New York law passed, Judd Legum, a liberal journalist, tweeted that it looks as if "House Democrats don't actually want Trump's tax returns" and "are doing pretty much everything possible to make sure they don't get them before November 2020." And the liberal resistance group Stand Up America demanded that Neal seek the president's state returns, saying that "any further delay is an injustice to the American people."

An aide to a Democratic member of Ways and Means told NBC News that "there has been widespread frustration from members of the committee at how slowly this process has moved."

"We respect his focus on moving rapidly on health care, tax policy and pensions, but at the same time many of us have tried to express the sense of urgency which we and our constituents feel about enforcing the law and obtaining Trump’s tax returns, and we just haven’t seen that sense of urgency reflected over the past six months," the aide added.

While many of his fellow chairmen ramped up oversight inquiries soon after the new Congress was seated in January, Neal waited before requesting the president's federal returns. After the Treasury Department refused to furnish them, Neal took months before suing the Treasury and the IRS for the documents.

Now, Neal says he won't request the state returns by using the new New York law because he believes doing so would harm his efforts at obtaining Trump's federal filings through the lawsuit, which could be tied up in the courts for years. Neal told Bloomberg News he thought requesting the state returns would boost the Trump administration's argument that Congress only wants them for political reasons and that, as chairman, he does not "have jurisdiction over New York taxes."

The New York law allows the chairmen of three congressional tax-related committees to request the state returns of public officials only after efforts to gain access to federal tax filings through the Treasury Department have failed. The bill states that any "legitimate task" of Congress is a valid reason to make the request, should efforts at the federal level be stonewalled.

Though state tax filings are not identical to federal returns, much of the same information appears on both.

Chris Rizek, an attorney at the Caplin & Drysdale tax law firm and former Treasury Department legislative counsel in the Clinton administration, told NBC News that Neal's concerns might "be a little bit overblown" with regard to how making the state request would affect his federal lawsuit.

"The whole point of the statute is to give Chairman Neal an alternative way to get some of the same information, and I think it's kind of separate," said Rizek, who also served as an attorney in the Department of Justice's tax division during the Reagan administration.

Neal's office did not return requests for comment.

House Speaker Nancy Pelosi, D-Calif., has publicly backed Neal's approach, as have some on his committee.

"Chairman Neal is consulting with the appropriate officials and is acting cautiously and judiciously," Rep. Gwen Moore, D-Wis., a Ways and Means member, said. "He is part of the solution, not the problem."

Other members have expressed willingness to use the New York law.

"Chairman Neal has conducted this investigation into the IRS' required review of the president’s taxes with diligence and integrity, and I trust in the process that has been unfolding with positive results so far," Rep. Judy Chu, D-Calif., a Ways and Means member, said in a statement. "The new law out of New York State is a new and interesting option that I believe should be considered and examined as we move forward."

Rep. Bill Pascrell, D-N.J., another Ways and Means member, expressed confidence Neal would be victorious in the lawsuit — but said he also was open to using the New York law.

"I appreciate what the New York legislature and Gov. Cuomo are trying to accomplish," Pascrell said. "We should investigate any tool provided us that might shed sunlight on Trump's tax return history, including his tax reporting practices and the results of any IRS audits."

Trump's team has signaled they will fight efforts to obtain the state returns should Neal opt to do so.

Meanwhile, the New York lawmakers who sponsored the legislation remain hopeful that Neal will take advantage of the new law.

State Sen. Brad Hoylman, a Democrat, said it gives "Congress a constitutional escape hatch should they not want to wait for the federal court case and its appeals process to be finalized, which potentially could take months to years."

"But, I leave it to the wisdom of the congressional tax committees to determine how they're going to utilize this legislation, if they are at all," he added.

Assemblyman David Buchwald, a Democrat, said Neal's remarks against using the legislation "were made before the (New York) bill became law, so it's appropriate to let Congress weigh things now that this law is on the books here in New York."