House Oversight and Government Reform Committee Chairman Rep. Darrell Issa (R-Calif.) right, has suggested that the Obama administration deliberately destroyed the e-mails. (Manuel Balce Ceneta/AP)

Two hearings this week heightened Republican frustration over missing e-mails that they believe could shed light on the Internal Revenue Service’s tea party controversy.

IRS Commissioner John Koskinen on Monday denied tipping off the White House about the lost records, and former IRS attorney Jennifer O’Connor, who now works for the White House, said Tuesday that she left the agency before it discovered the problem.

“I didn’t tell anybody,” Koskinen told the House Oversight and Government Reform Committee. “I was advised. I had no one I was going to tell.”

The commissioner also said the Treasury Inspector General for Tax Administration is investigating the missing records, and David Ferriero, the national archivist, told Tuesday’s panel that the IRS “did not follow the law” when it failed to inform the National Archives and Records Administration of the lost e-mails.

Koskinen’s testimony led to more questions than answers about how word of the missing e-mails spread to the West Wing in April. Congress, which has subpoenaed the records, learned about the matter on June 13.

Committee chairman Darrell Issa (R-Calif.) asked: “Did you cause someone to find out at the White House, or Treasury or your [inspector general]?”

“I did not,” Koskinen said. “And if you have any evidence of that, I’d be happy to see it.”

The committee is seeking ­e-mails from IRS official Lois Lerner, a key witness in the panel’s investigation. The agency claims to have lost many of the records after Lerner’s hard drive crashed in June 2011.

Issa has suggested that the Obama administration deliberately destroyed the e-mails to hide evidence that the IRS targeted conservative groups during the past two elections.

In a letter requesting O’Connor’s testimony last week, Issa said the former IRS attorney “likely knew or should have known” that many of Lerner’s e-mails were missing.

But O’Connor, who worked for the IRS from May 2013 through November 2013, said she was unaware of the problem during her tenure with the agency. “I did not know that her e-mails were missing and unrecoverable, or that her computer crashed,” she said.

The commissioner said that he first heard of the hard drive problem in February and that he learned in April that the data was not recoverable. He said he did not recall who told him about it.

The IRS has released e-mails showing that Lerner tried to recover her files with help from technical experts, including IRS forensic specialists.

Much of Monday’s hearing focused on technical aspects of the IRS’s system for backing up official e-mails, some of which are required by law to be archived.

Koskinen said he knew of no attempts by the IRS to retrieve Lerner’s files from a “disaster recovery tape” that automatically saves all of the agency’s e-mails over a six-month period. He explained that “extracting individual e-mails out of that is very costly and difficult.”

Monday’s hearing began in dramatic fashion, as Issa showed a video montage of Republican lawmakers demanding all of Lerner’s e-mails and Koskinen promising to deliver.

“I said I would provide all the e-mails — we are providing all the e-mails,” Koskinen said Monday, adding, “I never said I would provide e-mails we didn’t have.”

Koskinen’s remarks prompted indignation from Republicans, who suggested the IRS chief should have been more forthcoming about the lost records. “I have lost patience with you,” Issa said.

GOP frustration was also on display Friday with the House Ways and Means Committee, where Koskinen refused to apologize, saying the problem was due to “technical glitches” and Rep. Paul Ryan (R-Wis.) told him, “Nobody believes you.”

Koskinen suggested that the loss of e-mails could have been avoided with additional funding for IT upgrades, saying the IRS’s computers and backup systems are dated. He said that Congress has reduced the agency’s budget by $850 million over the past four years and that the House has proposed cutting it by an additional $350 million for 2015.

“Well, surely that will change in light of our deep and profound concern for what happened to Lois Lerner’s hard drive,” Rep. Gerald E. Connolly (D-Va.) said sarcastically.

Republicans said the IRS could have paid for upgrades with the tens of millions of dollars the agency spent on bonuses and conferences in recent years.

Lawmakers have criticized the IRS for paying performance awards to employees who owe taxes and for spending more than $4 million on a 2010 junket in Anaheim for 300 workers.

Rep. John F. Tierney (D-Mass.) apologized for the Republicans’ posture toward Koskinen.

“I don’t think I’ve seen a display of this kind of disrespect in all the time I’ve been here in Congress,” Tierney said. “It’s unfortunate that anybody would have to be subjected to it.”