WASHINGTON — U.S. Rep. Charles Boustany, who has looked into allegations of the IRS targeting conservative nonprofits for about two years, said the agency will face intensive congressional investigation after its leadership admitted to singling out some tea party-related groups for extra scrutiny.

Boustany, R-Lafayette, has examined the matter as the chairman of the House Ways and Means Subcommittee on Oversight and expressed concern Monday that former Internal Revenue Service Administrator Doug Shulman “flat-out denied” such concerns when Boustany asked him about it last year.

“This is worse than political partisanship; this is pure abuse of power,” Boustany said. “We’re not going to let them off the hook.”

The IRS story has picked up steam since Lois Lerner, the IRS official who oversees tax-exempt groups, on Friday apologized for the Cincinnati IRS office singling out tax-exempt applications to the IRS that included phrases like “tea party” or “patriots” dating back to 2010, although the practice later changed.

The admission came in advance of a U.S. Treasury Inspector General for Tax Administration report on the topic that is expected this week.

Boustany had previously sent a letter to acting IRS Commissioner Steven Miller for all communications on the issue without getting what he considered adequate responses.

Boustany is stopping short of calling for Miller’s resignation, which U.S. Sen. Marco Rubio, R-Fla., did on Monday. Boustany said more information is needed first about who knew what and when.

The applications for tax-exempt, 501(c)(4) status in recent years have become more controversial because such groups are considered social welfare organizations that are allowed to lobby, but they are not supposed to be politically focused.

President Barack Obama on Monday said he just found out about the matter on Friday and expressed outrage.

“If, in fact, IRS personnel engaged in the kind of practices that had been reported on and were intentionally targeting conservative groups, then that’s outrageous and there’s no place for it,” Obama said.

However, LSU law professor Phillip Hackney, argued that he believes the IRS was not showing political partisanship.

Hackney, until 2011, worked with Lerner at the IRS as a senior technician reviewer in the IRS’ Office of the Chief Counsel.

“I think it’s overblown,” Hackney said, noting that he was not speaking on behalf of LSU. “I think it’s kind of a tempest in a teapot.”

The IRS, under Lerner, has frequently targeted left-leaning groups in reviews, Hackney said.

Hackney argued that the IRS was only looking further into tax-exempt applications of groups that may have intended to be politically active beyond their nonprofit statuses and operate more like political action committees.

“I don’t believe they were targeting the tea party alone,” Hackney said. “They were right to be looking closely at tea party groups.”

While the IRS likely did so to act more efficiently, Hackney said, the IRS also should have been more aware of the ramifications of filtering out words such as “tea party.”

So the execution should have been better, he said, even if the intent was appropriate.

Even if there was no partisan intent, Boustany said, the filtering of conservative-aligned words “certainly gives it a political overtone.”

“The American people are already fearful enough of the IRS, and we have to ensure that the IRS is acting in an objective manner,” Boustany said.

Other members of the Louisiana delegation also weighed in on Monday, such as Sen. David Vitter, R-La., calling for a full audit of the IRS.

“An apology isn’t enough, and I’ll be going through the investigative report immediately once it’s released, but I think we need a full audit of the IRS to determine the full extent of who ordered the targeting of conservative groups,” Vitter stated.

U.S. Rep. Bill Cassidy, R-Baton Rouge, also called for greater investigations.

“It’s ironic that those who care most about protecting and preserving a constitutional form of government were investigated in an extra-constitutional way,” Cassidy stated.