House Ways and Means Committee Chairman Dave Camp told CNBC ahead of his panel's IRS scandal hearing on Friday that he wants to know who "hatched" the plan to target conservative groups seeking tax exempt status for extra scrutiny.
"The scale of it and the length of time, this was a pattern. This was a culture of discrimination where it was OK to go after conservative groups," the Michigan Republican said in a "Squawk Box" interview. "[But] progressive groups seemed to find the process just worked OK for them. That's what's troubling."
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Another member of the panel, Democratic Rep. Charles Rangel of New York, also appeared on the show, saying any talk of impeachment of President Barack Obama over this is "ridiculous."
"This is embarrassing for the president, but he's doing everything he can do," Rangel said. "In a bipartisan way, we want to see how this got started, and cut this cancer before it spreads."
Camp agreed, "We want to know who hatched this plan."
"We obviously need to dig a lot deeper," he said, "and find out who knew this, who authorized it, who thought of it, and why it was allowed to continue for so long."
Outgoing IRS Acting Commissioner Steven Miller and the Treasury inspector general investigating the complaints, J. Russell George, are scheduled to testify before Camp's panel—the first in a series of congressional inquiries including by the House Oversight and Government Reform and Senate Finance committees next week.
Miller was forced to resign Wednesday, and President Barack Obama has since appeared in public twice to condemn the IRS's actions and to promise full cooperation with lawmakers.
The president chose on Thursday top White House budget office aide Daniel Werfel to be acting commissioner of the Internal Revenue Service.
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The controller of the Office of Management and Budget, Werfel has served in Republican and Democratic administrations and was a point man on the controversial automatic spending cuts known as "sequestration." He'll officially start at the IRS next week.
Going forward Rangle said there are "three things we have to do" and they are "are tax reform, tax reform, and tax reform."
"There's no excuse of us not cleaning up this mess that's in this system," he added.