U.S. Rep. Dave Camp, R-Mich., chairman of the House Ways & Means Committee, and U.S. Senator Orrin Hatch, R-Utah, ranking member of the Senate Finance Committee, have called on New York Attorney General Eric Schneiderman to halt all exploratory efforts involving the activities of several businesses and nonprofit 501(c)(4) organizations.

These organizations, while similar to 501(c)(3) tax-exempt organizations, are permitted to lobby and engage in political activity, as long as it is consistent with the organization's purpose and is not the primary activity of the organization.

In a letter, the lawmakers questioned whether the attorney general's office was adhering to federal law in obtaining the tax returns for these groups, and said the state should direct all inquiries to the Internal Revenue Service.

"Clearly, federal tax law carefully and extensively safeguards the confidentiality of taxpayer information. Failing to follow the guidelines set forth in the [Tax Code] suggests an attempt to improperly compel disclosure of federally protected taxpayer information," the letter stated. "We, therefore, request that your office cease its efforts to obtain tax returns and tax return information directly from these groups. Your office should direct your inquiries instead to the IRS, which will promptly and appropriately process the request pursuant to federal law and procedure."