Bluntly declaring "I am angry" about the IRS scandal, President Barack Obama said late Wednesday that Treasury Secretary Jack Lew had forced out Steven Miller, the acting commissioner of the Internal Revenue Service. Speaking in the East Room of the White House, Obama called Miller's ouster "the first step" to prevent similar misconduct in the future and vowed to "do everything in my power" to make sure it never happens again.

Obama said he had reviewed the Treasury Department Inspector General's report that details how the IRS targeted conservative groups for special scrutiny when they applied for tax-exempt status.

"The misconduct that it uncovered is inexcusable. It's inexcusable, and Americans are right to be angry about it and I am angry about it," the president said in a brief prepared statement. "I will not tolerate this kind of behavior in any agency—but especially in the IRS, given the power that it has and the reach that it has into all of our lives."

Obama said the "responsible parties" will be held accountable. Lew "took the first step by requesting—and accepting—the resignation of the acting commissioner of the IRS because given the controversy surrounding this audit, it's important to institute new leadership that can help restore confidence going forward," Obama added.

The president's statement from the East Room of the White House came a little more than an hour after a meeting with senior Treasury Department officials to discuss the controversy.

Obama said he had directed the agency to implement recommendations from the inspector general—the Treasury's internal watchdog—to ensure no repeat of the "outrageous" misconduct. "The good news is it’s fixable," he said.

Looking to Capitol Hill, where lawmakers of both parties have denounced the IRS' behavior, Obama promised: "We will work with Congress as it performs its oversight role, and our administration has to make sure that we are working hand-in-hand with Congress to get this thing fixed."

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Lawmakers, in turn, should "treat that authority with the responsibility it deserves and in a way that doesn’t smack of politics or partisan agendas," Obama said. He said Washington must "make sure that the laws are clear" and suggested that "too much ambiguity" may have played a role.

“I’ll do everything in my power to make sure nothing like this happens again—by holding the responsible parties accountable, by putting in place new checks and new safeguards, and, going forward, by making sure that the law is applied as it should be: In a fair and impartial way," Obama said.

Republican Senate Minority Leader Mitch McConnell expressed skepticism.

“More than two years after the problem began, and a year after the IRS told us there was no problem, the President is beginning to take action," the Kentucky lawmaker said. "If the president is as concerned about this issue as he claims, he’ll work openly and transparently with Congress to get to the bottom of the scandal—no stonewalling, no half-answers, no withholding of witnesses."

Congress is "determined to get answers, and to ensure that this type of intimidation never happens again at the IRS or any other agency," McConnell said.

Democratic Sen. Patrick Leahy of Vermont was blunter, tweeting:

The President is right to dismiss the #IRS chief, and cleaning house may take more firings. — Sen. Patrick Leahy (@SenatorLeahy) May 15, 2013

On Wednesday, Attorney General Eric Holder promised angry lawmakers that the Justice Department will undertake a national investigation into the IRS wrongdoing.

"We will take a dispassionate view of this," said Holder, who faced tough questioning from the House Judiciary Committee. "This will not be about parties ... anyone who has broken the law will be held accountable."

Holder said he had launched an investigation last Friday into why the IRS subjected conservative groups to more review when they applied for tax-exempt status. The IRS inspector general's report said that a group of low-level staffers in an Ohio office were responsible, and a top IRS official has apologized on their behalf.

But Holder promised that the investigation will look well beyond Ohio, and suggested that civil rights laws could have been violated.

Rep. Bobby Scott, D-Va., asked Holder at the hearing whether an "apology" from the IRS protected them from criminal prosecution. Holder answered, "No."

The Obama administration is under fire over the IRS, the president's handling of the Sept. 11, 2012, terrorist attack in Benghazi, Libya, and the Justice Department's secret collection of telephone records of Associated Press reporters and editors.

Republicans have been hammering Obama on all three matters. While Democrats have largely defended him—and former Secretary of State Hillary Clinton—on Benghazi, they have joined their GOP colleagues in denouncing the IRS and in expressing deep concerns about the AP phone records.

On Monday, Obama dismissed Republican charges of a cover-up in the Benghazi situation as a "sideshow" lacking any merit. He has yet to comment directly on the AP issue.