Sen. John ThuneJohn Randolph ThuneGOP pushes to change Senate rules for Trump With shutdown nearing, focus turns to Rand Paul Spending package extends FAA through September MORE (R-S.D.) said Sunday that the Department of Justice should appoint a special prosecutor to investigate recent reports the IRS sought to audit Sen. Chuck GrassleyCharles (Chuck) Ernest GrassleyGrassley on Trump calling Putin: 'I wouldn't have a conversation with a criminal' Lawmakers zero in on Zuckerberg GOP senator blocking Trump's Intel nominee MORE (R-Iowa).

“If we can’t get these investigations that Congress is trying to do concluded, we need a special prosecutor to look into this,” Thune said. “The American people deserve answers, and they’re not getting them.”

Thune said recent emails revealed former IRS official Lois Lerner was using her power to advance a political agenda by targeting the Republican senator.

“We’re all very concerned when we hear that the IRS, in addition to targeting conservative political groups, may be targeting conservative senators who’ve been critics of the IRS,” Thune said on C-SPAN’s “Newsmakers”. “It’s just again another example of an agency with a bunch of people who really have an agenda that has run amok.”

House Republicans have been investigating reports that the IRS targeted Tea Party-affiliated groups under Lerner’s watch, and the latest emails about Grassley were released last week.

“This latest revelation about Sen. Grassley is sort of piling on, in my view, a very cumulative amount of evidence that these guys were completely using that agency, which has tremendous power on people’s lives — tremendous power — the ability to ruin and destroy people’s lives — that they were using it for political purposes,” Thune said. “That’s just wrong.”