The man appointed to temporarily run the embattled Internal Revenue Service told a House subcommittee on Monday that he received orders from President Obama to "get to the bottom" of a widening scandal involving the agency's targeting of conservative groups.

Acting IRS Commissioner Daniel Werfel, making his first Capitol Hill appearance, told a House Appropriations subcommittee that he spoke to Obama for about 20 minutes in mid-May in which "he articulated my mission here at the IRS."

Obama told Werfel to "conduct an accountability review" that would both restore America's trust in the IRS and hold accountable those responsible for targeting conservative groups seeking federal tax exemption.

But Werfel, who said he was recruited for the job by White House Chief of Staff Denis McDonough, now faces a growing number of problems at the IRS. A new audit found the agency spent $50 million on 220 conferences over two years beginning in 2010. And in the midst of the hearing, J. Russell George, the inspector general investigating the IRS, announced he will issue yet another audit, this one due in the fall, that will expose the agency's policy of issuing bonuses to employees.

"It seems we have a new misstep every day at the IRS," House Appropriations Committee Chairman Harold Rogers, R-Ky., said. "I'm very troubled at what may come to light next."

The audit on IRS conference spending is due to be released Tuesday and Congress is planning several more IRS-focused hearings this week that will delve into both the targeting of conservative groups and the report on conference spending.

Werfel, who said he is often tapped to step in and fix agency problems, called the IRS targeting of conservatives "completely inexcusable." He said he would take immediate action to correct problems, including instituting the changes recommended in George's audit.

But Werfel rejected lawmakers' call for a special prosecutor to investigate the IRS, saying that there are already four independent investigations into the targeting underway, including one by the Justice Department.

"What I would suggest is let's monitor that and see if we are getting the progress this committee is demanding," Werfel told lawmakers.

While the appropriations hearing focused on the IRS conference spending, a lot of the testimony centered on the targeting and the mystery of who ordered it.

Werfel said he has not yet asked any of the lower level IRS employees who carried out the targeting if anyone ordered them to do it. Evidence is mounting the orders may have come from the agency's Washington headquarters.

One Democrat on the panel, Rep. Jose Serrano, of New York, suggested lawmakers are wasting time trying to connect the IRS targeting to the Obama administration.

"I think we're spending too much time trying to figure out if someone said, do it, rather than why it was done and who did it," Serrano said.

George, the auditor who is still investigating the matter, said he so far has no evidence connecting the targeting to the White House, but said it was reminiscent of IRS targeting during the Nixon administration, when the tax agency was used to attack political enemies.

"During the Nixon administration, there were attempts to use the Internal Revenue Service in manners that might be comparable in terms of misusing it," George said, adding later, "But this is unprecedented."