WASHINGTON (Reuters) - Congressional Democrats are frustrated with the U.S. Internal Revenue Service's handling of a year-old, Republican-led investigation of the tax agency's scrutiny of Tea Party-aligned political groups, said a senior Democrat and aides on Thursday.
The head of the IRS is set to testify on Friday and Monday on the affair before two Republican-controlled panels.
Democratic Representative Lloyd Doggett said there was no level of responsiveness, in a probe with clear political overtones, that would satisfy Republicans.
At the same time, Democrats said, the IRS made errors that helped perpetuate the damaging inquiry, which leapt back into the headlines last week after the IRS said it had lost emails written by former agency official Lois Lerner.
"I don’t approve of either Lois Lerner or the way IRS has handled this," Doggett told Reuters in an emailed response to questions, adding, "No response will satisfy Republicans so obsessed with finding a conspiracy that they are probably already trying to connect Lois Lerner with Benghazi."
IRS Commissioner John Koskinen is slated to testify before the House Ways and Means Committee on Friday, and the House Oversight and Government Reform Committee on Monday.
The panels' chairs, Republicans Dave Camp and Darrell Issa, have competed for control of the probe, aides said, with both pressing the IRS for information in search of an elusive prize - a link to the White House.
House Speaker John Boehner on Thursday questioned the IRS's credibility. "Who could possibly believe that they've lost two critical years' worth of emails for the central figure in this investigation?” he asked.
A House Democratic staffer familiar with the investigation, who asked not to be named, said IRS handling of it has been "forehead-slapping ... unforced error after unforced error."
The IRS declined to comment.
Camp's panel said on June 13 that the IRS had informed committee investigators that certain emails by Lerner from January 2009 to April 2011 had been lost in a computer crash.
Asked about the emails on Wednesday by reporters, White House spokesman Jay Carney said: "IT professionals worked to restore Lerner’s hard drive but were unable to do so. Nonetheless, the IRS has or will produce 24,000 Lerner e-mails from this 2009-2011 time period largely from the files of the other 82 individuals."
Carney said the IRS has furnished Republican investigators with 750,000 pages of documents. He said Camp asked for any emails between Lerner and the White House.
"We did, in fact, do a search for all communications between Lois Lerner and any person within the Executive Office of the President for this period. We found zero e-mails," he said.
The investigation dates to May 2013, when Lerner unexpectedly apologized in public for what she called "inappropriate" scrutiny by the IRS of non-profit conservative groups, some aligned with the Tea Party. Outraged Republicans accused the IRS of unfairly singling out conservative groups' non-profit status applications for extra scrutiny.
(Additional reporting by Patrick Temple-West. Editing by Douglas Royalty)