The IRS has released a list of more than 400 nonprofit groups the agency claims it may have treated improperly, including by applying extra scrutiny in the case of conservative groups that were seeking tax-exempt status.

The list, which was revealed as part of a recent federal court filing, includes more than 100 groups that had not been made public during a previous investigation by the Treasury inspector general.

The IRS produced the list after being asked by the U.S. District Court for the Southern District of Ohio, which said the full universe of entities that might have been subject to IRS targeting must be made clear. It makes up the full list of groups that could find relief in an ongoing lawsuit against the IRS in that court.

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The list is significantly longer than the one produced in May 2013, when an OIG reported concluded the IRS had targeted 298 groups. Part of the reason for that could be the ideologically diverse range of groups included: The agency is claiming it also targeted several progressive organizations.

Just 12 of the groups include the word "progress," while three include "occupy," a term associated with the Occupy Wall Street movement.

In contrast, more than 100 include "tea," "patriot," or a reference to the Constitution. While some groups were based in Washington, D.C., like the American Legislative Exchange Council and the Libre Initiative, a majority were state-based organizations.

The NorCal Tea Party Patriots are leading a class action suit on behalf of those who were targeted. Another 40 groups that were targeted but that opted out of the suit were not included on the list.

Edward Greim, an attorney leading the case for the plaintiffs, said the size of the new list raises new questions about the scope of the agency's wrongdoing.

"First, evidence in this case has revealed that the IRS continued its targeting even after TIGTA [Treasury's Inspector General for Tax Administration] began its investigation and released its report, slightly increasing the number of affected groups. Second, and equally significant, the class notice process is designed to reach all potential members of the class," Greim said.

Greim also said he suspects that the IRS may have purposefully expanded the list of entities that may have been targeted, in order to show it was not only applying extra scrutiny to conservative groups.

"[A] very real possibility — if not probability — exists that the IRS modified its targeting in light of the investigations, packing its own internal lists of targeted groups to support its preferred narrative, including by adding ideologically diverse groups," he said. "Any such conduct may have tainted the list released yesterday, since it originally derives from the IRS's internal records," he said.

Greim said that might explain why not all the groups on the list were actually targeted by the IRS. He noted examples like the League of Women Voters, of which three chapters are included on the list: California, Hawaii, and Vermont.

The case followed the 2013 revelation that the IRS for years targeted conservatives nonprofit groups improperly, subjecting them to excessive audits and delaying their applications for nonprofit status. Lois Lerner, who headed the agency's tax-exempt division, resigned over the scandal in September of that year.

House Republicans are still pushing for the impeachment of IRS Commissioner John Koskinen partially on the basis that he obstructed a congressional probe into the issue.

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The IRS is facing other lawsuits stemming from the issue as well. The American Center for Law and Justice is spearheading an appeal before the federal court for Washington, D.C. on behalf of plaintiffs who say the IRS is still engaged in targeting, while Cause of Action is seeking to uncover what role the White House may have played in coordinating with the agency.