IRS Commissioner John Koskinen told a House panel Wednesday it will "take years" to produce evidence that the agency targeted Tea Party and other conservative groups.
The House Oversight Committee has subpoenaed thousands of documents, including emails to and from former IRS official Lois Lerner dating back to 2009.
Testifying before the panel, Koskinen noted that his office has provided more than 1 million pages of documents to congressional committees since the investigations began last spring.
Koskinen explained the process would be lengthy because, by law, the agency must remove sensitive personal information about taxpayers from any documents they give the oversight panel.
House lawmakers, however, suggested the agency is more concerned about stemming the fallout from the scandal.
"Does a nonpartisan or nonpolitical agency withhold documents requested during a congressional investigation? The IRS does and did," Politico quoted Committee Chairman Darrell Issa, R-Calif.
"You've been more concerned with managing the political fallout," he charged.