WASHINGTON (Reuters) - Attorney General Eric Holder said on Tuesday he had ordered the FBI to open a criminal probe in a growing scandal over the Internal Revenue Service's targeting of conservative political groups for extra tax scrutiny.
Holder announced the Justice Department investigation as the tax agency's embattled acting commissioner, Steven Miller, traveled to Capitol Hill for meetings on the scandal amid Republican lawmakers' calls for his resignation.
The scandal has added to a sense of a White House under siege as President Barack Obama, who has promised to hold any IRS wrongdoers accountable, grapples with an array of domestic and foreign policy controversies that threaten his second-term agenda.
On Friday an IRS official revealed that the agency had inappropriately singled out conservative groups, some associated with the Tea Party movement, for extra scrutiny of their claims for tax-exempt status.
"I have ordered an investigation," Holder told reporters at a news conference. "FBI is coordinating with the Justice Department to see if any laws were broken."
He said that the actions disclosed so far "were, I think as everyone can agree, if not criminal, they were certainly outrageous and unacceptable, but we are examining the facts to see if there were criminal violations."
There were growing calls on Capitol Hill for the resignations of Miller and Lois Lerner, head of the IRS tax-exempt organizations office. Lerner apologized on behalf of the agency when she revealed the targeting of conservative groups last week.
Conservatives had complained about mistreatment by the IRS for years.
Miller was due to meet Senator Max Baucus, the Democratic chairman of the tax-writing Senate Finance Committee who has promised an investigation by his panel.
Senate Republican leader Mitch McConnell of Kentucky urged Obama to make all who knew about IRS misconduct available for questioning, and said there should be "no more stonewalling."
"Heads need to roll today," said Republican Representative Vern Buchanan of Florida, a member of the House of Representatives Ways and Means Committee.
The panel oversees the IRS and is scheduled to hold a hearing on the scandal on Friday.
Despite efforts by some conservative commentators to cast the IRS troubles as something akin to the Watergate scandal of the 1970s - or to former President Richard Nixon's use of the IRS to target his political enemies - there was no sign of White House involvement in the matter.
White House spokesman Jay Carney said the results of independent investigations must be known "before we can jump to conclusions about what happened, whether there was a deliberate targeting of groups inappropriately and, if that's the case, what action should be taken."
The IRS - which is supposed to be a nonpartisan agency - has suddenly found itself dragged into partisan politics at a time when it is also under increasing pressure to make rulings on campaign finance issues and matters related to Obama's healthcare overhaul.
Additional reporting by Patrick Temple-West, Thomas Ferraro, Susan Heavey and Laura MacInnis; Editing by Xavier Briand