WASHINGTON -- The House Ways and Means Committee chairman called for a special prosecutor to probe the Internal Revenue Service's loss of emails from the time the agency gave extra scrutiny to Tea Party groups seeking tax-exempt status.

"We are missing a huge piece of the puzzle," committee Chairman Dave Camp said at a hearing Friday in Washington. The two years of missing emails cover the "very peak" of the IRS scrutiny, the Michigan Republican said. "How convenient for the IRS and the administration."

The IRS said last week that a computer crash, combined with routine recycling of backup tapes, meant it couldn't recover many emails written from 2009-11 by Lois Lerner, director of exempt organizations at the time.

IRS Commissioner John Koskinen told the committee Friday that a computer hard drive was destroyed and recycled in line with normal processes, prompting audible groans from Republicans on the panel.

The Obama administration also released a letter that said Lerner didn't exchange any emails with White House officials during that period.

Reviewers "were unable to identify any communications between Lois Lerner and persons within" the president's executive office, W. Neil Eggleston, a White House counsel, said in a letter Wednesday to Camp and Senate Finance Committee Chairman Ron Wyden. The letter didn't explain how officials came to that conclusion.

White House spokesman Josh Earnest told reporters Friday that the Obama administration opposes appointing a special prosecutor in the case.

"I'm not sure there's a whole lot left to discover here," Earnest said, adding that there have been "a long list of claims and conspiracy theories by Republicans that just haven't panned out."

Republicans have said the IRS gave extra scrutiny to some Tea Party-related groups asking for tax-exempt status.

IRS documents said that after Lerner's computer hard drive crashed in 2011, experts at the IRS Criminal Investigations forensic lab unsuccessfully attempted to recover its contents. In a July 19, 2011, email, Lerner told the technicians that there were "irreplaceable" documents that she wanted to retrieve.

Koskinen read a statement describing the computer crash and IRS response. Camp responded that the statement didn't include an apology.

"I don't think an apology is owed," Koskinen responded.

Minutes later, Georgia Democrat John Lewis apologized -- to Koskinen -- for the way the hearing was being conducted. Democrats said it was an inquisition.

That set off Rep. Paul Ryan.

"The apology that ought to be given is to the American taxpayer, not a government agency that's abusing power," the Wisconsin Republican said. "I am sitting here listening to this testimony and, I just, I don't believe it. That's your problem, nobody believes you."

Ryan went on. The IRS hasn't been forthcoming, he said, and has a track record that makes people doubt it can be impartial. "I don't believe you," he said, "this is incredible."

"I have a long career. That's the first time anybody has said they do not believe me," Koskinen responded.

"I don't believe you," Ryan said.

The controversy centers on so-called social welfare groups, which under U.S. tax law don't have to disclose their donors. That has made them an attractive vehicle for anonymous involvement in politics.

Groups organized under Section 501(c)(4) of the U.S. tax code must be organized "exclusively" to promote social welfare. The IRS has interpreted that to mean such groups can't have politics as their primary purpose, a decision that has led to disputes over the meaning of "politics" and "primary."

Democrats called Friday's hearing an exercise in letting Republicans air conspiracy theories.

"There is absolutely no evidence to show that Ms. Lerner's computer crash was anything more than equipment failure," said the panel's top Democrat, Sander Levin of Michigan.

"Was her computer crash a conspiracy? No," Levin said. "Was the Internal Revenue Service's system for backing up its email system entirely underfunded and wholly deficient? Yes."

Illinois Republican Peter Roskam said Koskinen may decide it was a mistake to accept the IRS commissioner job, musing that he may leave in six months or a year.

Koskinen said he is "firmly committed" to serving his full term, which expires in November 2017.

Koskinen said that any emails recovered from inside the agency will be shared with lawmakers as they were found.

Information for this article was contributed by Richard Rubin and Roger Runningen of Bloomberg News; and by Eileen Sullivan, Jack Gillum and Stephen Ohlemacher of The Associated Press.

A Section on 06/21/2014