By Patrick Temple-West and Kim Dixon
WASHINGTON (Reuters) - A senior Republican lawmaker on Friday issued a subpoena to Treasury Secretary Jack Lew seeking documents related to a nearly three-month old congressional probe of the Internal Revenue Service's treatment of conservative political groups.
In a move to keep the pressure on the Obama administration, Darrell Issa, the top Republican on the oversight committee of the U.S. House of Representatives, said the IRS is delaying his investigation, leaving him no choice but to issue the subpoena.
"You are slow-rolling us," Issa, a California Republican, said to IRS acting chief Danny Werfel at a hearing on Friday. "You frustrated this committee."
Werfel defended the IRS, saying it is legally bound to honor taxpayer protections before releasing documents. "Any indication that we are standing in the way of discovery is just not true," Werfel said.
The IRS operates under the Treasury Department. In the months ahead, the Senate will need to consider confirming President Barack Obama's new IRS commissioner nominee, John Koskinen, who was named on Thursday.
Several committees of Congress are looking into allegations that the IRS unfairly scrutinized conservative political groups' applications for tax-exempt status in 2010-2012. A report by an IRS watchdog in May faulted the agency's conduct on several levels.
Werfel, appointed by Obama to run the tax agency in the days after the scandal broke, said at the hearing that the IRS has assigned 70 lawyers full-time to go through millions of documents.
After months of digging, congressional staffers have not produced evidence linking Obama and the White House to low-level IRS employees first involved in flagging the tax-exemption applications of conservative groups for closer review.
Republicans have recently focused on IRS Chief Counsel William Wilkins. His office learned of the screening of Tea Party-related groups fairly early on, but no evidence has been uncovered linking Wilkins, an Obama appointee, to the activity.
(Editing by Kevin Drawbaugh and Phil Berlowitz)