The U.S. Chamber of Commerce—long a proponent of unfettered political spending—praised the IRS on Tuesday for announcing it no longer will require certain nonprofits to disclose their donors to the agency.

"We applaud Treasury's decision to rescind the donor disclosure requirements for some nonprofit groups," Chamber spokesperson Blair Holmes said in a statement.

But liberal advocacy group Common Cause asked Congress to investigate the move, citing the threat of foreign money potentially corrupting tax-exempt groups as highlighted by the recent arrest of a Russian woman in connection with an alleged effort to influence the National Rifle Association.

Law firm Covington & Burling described the action as "significant and unexpected," but noted the IRS' position that the disclosures are not mandated by law and are an undue record-keeping burden for nonprofit groups as well as the agency.

The decision applies to most categories of tax-exempt entities required to file an IRS Form 990—including trade groups, labor unions and 501(c)(4) "social welfare" organizations—but not groups incorporated as 501(c)(3)s, including charities and many professional associations. Up until now, the IRS has required the donor disclosure on 990s but has redacted it before releasing the forms to the public.

The Chamber called it a free-speech issue.

"This action will help ensure that sensitive donor information will not fall into the hands of those who wish to suppress the First Amendment right to free speech," Holmes said. "The U.S. Chamber strongly supports the right of all organizations—no matter their ideological or political persuasion—to participate vigorously in our nation's important policy conversations.

"We now encourage Congress to take action to remove onerous donor disclosure requirements for tax-exempt organizations that were not covered by this important announcement," Holmes said.

But Common Cause called for hearings, saying in a statement it had sent letters to the House Ways and Means Committee and the Senate Finance Committee urging probes.

"As the indictment and arrest of Mariia Butina made very clear, the Russian government is already trying to use organizations like the National Rifle Association to influence U.S. policy and as citizens we need to know more, not less about who is funding them," Common Cause President Karen Hobert Flynn said in the statement.

"At a time when there is a very real threat of foreign money being wielded illegally to sway our elections we should not be stripping the IRS of important tools to safeguard the system from that threat," she said.

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