WASHINGTON (AP) -- President Barack Obama's spokesman says the White House is facing "legitimate criticisms" for its shifting accounts about who knew what about the Internal Revenue Service's targeting of conservative political groups, and when they knew it.

Press secretary Jay Carney's acknowledgement Wednesday was an attempt to stem a growing narrative that the White House has bungled its response to the IRS controversy, even though the White House appears to have had no direct role in the agency's targeting of conservative political groups.

"There have been some legitimate criticisms about how we're handling this," Carney told reporters during his daily briefing. "And I say 'legitimate' because I mean it."

The criticism of the White House has largely focused on its evolving story about who in the White House knew about the IRS targeting before it became public May 10. Carney on Wednesday attributed the changing accounts in part to an attempt by the White House to provide the public information quickly, even before the full details are known.

"Quickly and comprehensively are not objectives that always meet," he said. "Our approach is we get the information we have to you, and as we get more information, we fill in the details."

Since the IRS targeting of conservative groups became public, the White House's primary focus has been making clear that Obama had no advanced knowledge of the agency's actions or an independent audit of the activity. Carney and other White House advisors say the president learned about the targeting like the general public -- from news reports.

However, Carney has struggled to provide full accounts of who on the president's staff may have known about the politically explosive IRS activity before the president.

In his first account last week, Carney said White House Counsel Kathryn Ruemmler was told "very broadly" on April 24 about the inspector general's audit into the IRS office at the center of the targeting controversy.

But on Monday, Carney said staff in Ruemmler's office first learned of the impending IRS report on April 16. After Ruemmler was told, Carney said she then alerted White House chief of staff Denis McDonough, deputy chief of staff Mark Childress and other senior White House officials.

Carney continued Wednesday to withhold the names of those other staffers, saying he "can't account for every conversation that might have been had."

The shifting stories have created friction between Carney and reporters during his daily briefings. However, the press secretary took a softer tone Wednesday, calling reporters "smart" and "good at your jobs."

Of course, Carney may have had another reason for his sunnier disposition. Wednesday marked his 48th birthday.

"This is how I chose to spend it," he joked as he fielded questions from reporters.

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