Three congressional committees have planned hearing into what interaction, if any, the IRS had with Treasury officials or the White House. Beginning in 2010, the IRS singled out conservative groups that were applying for tax exempt status according to a Treasury Department Inspector General report. NBC's Lisa Myers reports.

Attorney General Eric Holder told reporters Tuesday that he recused himself last year from any involvement in an investigation of national security leaks.

Holder also announced Tuesday that he has ordered an investigation to see if there were criminal violations in the Internal Revenue Service scrutiny of conservative political groups that had sought non-profit status.

Deputy Attorney General James Cole, who approved getting the AP's phone records to track down the person that leaked classified information, said it was a last-resort effort after having conducted hundreds of interviews. NBC's Pete Williams reports

On the leaks case, Holder – who is slated to testify before the House Judiciary Committee Wednesday afternoon -- reminded reporters that he testified to a congressional committee last year that he had recused himself to avoid the appearance of a conflict of interest.

The Associated Press reported Monday that phone records of its reporters and editors had been subpoenaed and seized in that probe.

Holder said decisions in that investigation were being made by Deputy Attorney General James Cole and “the deputy attorney general would have been the one who ultimately had to authorize the subpoena that went to the AP.”

He added that since he was recused from the investigation, “I’m not familiar with all that went into the formulation of the subpoena.”

He also said he could not explain why voluntary cooperation wasn’t sought from the Associated Press before the subpoena was executed.

US Attorney General Eric Holder says he's asked the FBI to investigate the "outrageous and unacceptable" behavior at the IRS, and to see if any criminal actions were taken by the agency.

“I am confident that the people who are involved in this investigation, who I know for a great many years and who I’ve worked with for a great many years, followed all of the appropriate Justice Department regulations and did things according to DOJ rules,” Holder said.

He added that it “certainly not the policy of this administration” to target reporters. What has been done in the leaks investigation was, he said, “not as a result of a policy to get the press.”

Referring to the leaks of national security information, Holder said, “This was a very, very serious leak. I’ve been a prosecutor since 1976 – and I have to say that this is among, if not the most serious, in the top two or three most serious leaks that I’ve ever seen. It put the American people at risk – and that is not hyperbole.”

Trying to find out who leaked the information “required very aggressive action,” Holder said.

Senate Majority Leader Sen. Harry Reid, D- Nev., on Tuesday joined other congressional critics of the Justice Department’s search of SAP’ phone records telling reporters “I have trouble defending what the DOJ did. It’s inexcusable. There is no way to justify this.”

In a letter to Holder on Monday, Associated Press President and Chief Executive Officer Gary Pruitt said, "There can be no possible justification for such an overbroad collection of the telephone communications of The Associated Press and its reporters.” Pruitt complained that the records could “disclose information about AP's activities and operations that the government has no conceivable right to know."

In a response, Cole wrote to Pruitt Tuesday that seeking phone records from media organizations “is undertaken only after all other reasonable alternative investigative steps have been taken.” He said that the Justice Department sought the AP phone records only after a comprehensive investigation which included conducting over 550 interviews and reviewing of tens of thousands of documents.