WASHINGTON—The Internal Revenue Service said a former official's 2011 computer crash significantly hampered its efforts to dig up correspondence requested as part of a congressional review of the agency's treatment of conservative groups.
The IRS said it is providing more emails to lawmakers and is doing its best to reconstruct correspondence from the former executive, Lois Lerner, who retired as the controversy unfolded last year. Its effort, which has included searching email of other senders and recipients, resulted in an additional 24,000 emails that are being provided to lawmakers, the agency said in a summary of its actions.
House Republicans investigating the IRS controversy reacted unhappily to the news of Ms. Lerner's computer crash.
"The fact that I am just learning about this, over a year into the investigation, is completely unacceptable and now calls into question the credibility of the IRS's response to congressional inquiries," House Ways and Means Committee Chairman Dave Camp (R., Mich.) said. "There needs to be an immediate investigation and forensic audit by the Justice Department as well as the inspector general."
Mr. Camp said the IRS couldn't provide Lerner emails to and from people outside the agency, "conveniently" feeding the impression she "acted alone." He called for an administration-wide search for her emails. House Oversight and Government Reform Chairman Darrell Issa (R., Calif.) said, "If there wasn't nefarious conduct that went much higher than Lois Lerner in the IRS targeting scandal, why are they playing these games?"
Ms. Lerner herself unsuccessfully tried to get agency technicians to reconstruct her hard drive at the time it crashed, the IRS said.
Ms. Lerner is a former head of the agency's exempt-organizations division. The House of Representatives recently voted to hold her in contempt of Congress after she declined to testify at hearings and cited her Fifth Amendment privilege against self-incrimination.
She has said she did nothing wrong in connection with conservative tea-party groups' applications for tax-exempt status. Many of the applications were subjected to heightened scrutiny starting in 2010, at a time when nonprofit groups were becoming more politically active in elections.
Congressional Democrats have argued that some liberal groups eventually were caught up in the IRS net as well.
In a statement, the IRS said that it has made "unprecedented efforts" to comply with congressional demands for documents and information concerning the targeting. The effort has involved more than 250 IRS employees working more than 120,000 hours at a cost of almost $10 million.
Counting information already provided, "investigators have—or will soon have—a total of 67,000 emails sent or received by Ms. Lerner," the IRS said.
The agency added that it is working with Congress and "has remained focused on being thorough and responding as quickly as possible to the wide-ranging requests from Congress while taking steps to protect underlying taxpayer information."