The House Ways and Means Subcommittee on Oversight has demanded that the IRS provide by Wednesday all communications involving the words "tea party," "conservative" or "patriot."
The committee also is demanding the names and titles of all individuals who were involved in targeting conservative non-profit groups for extra scrutiny, CNS reported.
The tax-collecting agency admitted on Friday that conservative groups had been improperly targeted and made to comply with cumbersome requests for information outside normal IRS procedures.
But the agency blamed the actions on a few low-level employees in its Cincinnati offices.
On Sunday, Republicans blasted the agency for broadly singling out conservative groups, or any political policy-minded groups, for that matter.
"This is something we cannot let stand. It needs to have a full investigation," House of Representatives Intelligence Committee Chairman Mike Rogers, a Michigan Republican, said on "Fox News Sunday."
"I don't care if you're a conservative, a liberal a Democrat or a Republican, this should send a chill up your spine," Rogers added.
"This is truly outrageous and it contributes to the profound mistrust that the American people have in government," Sen. Susan Collins, a Maine Republican, said on CNN's "State of the Union." "The president needs to make crystal clear that this is totally unacceptable in America."
Collins said she also doubted the IRS's claim that the groups were targeted as part of an "inappropriate" organizing technique by a few bureaucrats in the agency's tax-exempt section, rather than for political reasons.
"I just don't buy that this was a couple of rogue IRS employees. After all, groups with "progressive" in their names were not targeted similarly," Collins said.
"If it had been just a small group of employees, then you would think that the high-level IRS supervisors would have rushed to make this public, fire the employees involved and apologized to the American people and informed Congress," she said.
Rep. Rogers said an outside investigation was needed to get to the root of the matter, referring to IRS statements last year that no groups had been targeted for additional scrutiny.
"I don't know where it stops or who's involved ... (The investigation) has to be external. It's clearly shown that they can't do it themselves. And I think Congress needs to have that oversight," Rogers said.
The Treasury Department's inspector general for tax administration is to release a report on its investigation into the issue within a few days.
Rep. Darrell Issa, a California Republican, has vowed to investigate, and the House Oversight and Government Reform committee he chairs has the power to issue subpoenas.
In an exclusive, the Associated Press revealed on Saturday that a federal watchdog's upcoming report will say that senior Internal Revenue Service officials knew agents were targeting tea party groups as far back as 2011.
Lois G. Lerner, who heads the IRS division that oversees tax-exempt organizations, found out at a meeting on June 29, 2011 that groups were being targeted, according to the watchdog's report.
At the meeting, she was told that groups with "Tea Party," ''Patriot" or "9/12 Project" in their names were being flagged for additional and often burdensome scrutiny, the report says. The 9/12 Project is a group started by conservative radio and TV personality Glenn Beck.
The disclosure contradicts public statements by former IRS Commissioner Douglas Shulman, who repeatedly assured Congress that conservative groups were not targeted. He at the time described the communications between the IRS and conservative groups as the "normal back-and-forth that happens with the IRS."
Meanwhile, the committee has released a timeline of the interactions and a list of 10 questions it plans to ask the agency at an upcoming hearing.
That timeline, Fox reports,
includes Rep. Charles Boustany, chairman of Ways and Means Subcommittee on Oversight, sending a letter to Shulman on Oct. 6, 2011, for information “regarding the tax-exempt sector.” It ends on March 12, 2012 when the IRS wrote back “with no mention of knowledge of targeting conservative groups.”
Fox reports that some of the questions that are expected to be asked include: "What steps, if any, has the IRS taken to ensure that the targeting of individuals and organizations does not occur in the future?" and "When was the IRS commissioner made aware of these unlawful practices, what steps were taken, if any, to halt the harassment of conservative organizations? And "Who was disciplined regarding these practices, if anyone?"
Lerner instructed agents to change the agency's criteria for flagging groups "immediately," the report says.
The Associated Press and Reuters contributed to this report.
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