Current and former IRS officials will face a barrage of questions this week as they testify before Congress about the agency’s scrutiny of conservative groups applying for tax-exempt status.

Although the Ways and Means Committee subjected the outgoing leader of the IRS, Steven Miller, to intense questioning on May 17, committee hearings this week could be even more intense, as lawmakers dig deeper into the details of the controversy that has embroiled the revenue-collecting agency.

Miller, who last week blamed the IRS’s targeting of conservative organizations on poor management and “foolish mistakes” by low-level employees, will face skeptical lawmakers again Tuesday, this time at the Senate Finance Committee. Former IRS Commissioner Douglas Shulman, who led the agency when most of the actions in question took place, will make his first public appearance at the hearing.

Shulman, appointed by President George W. Bush to a five-year term that expired last year, will testify Wednesday before the House Oversight and Government Reform Committee. Joining him will be Neil S. Wolin, the deputy secretary of the Treasury Department, and Lois Lerner, the director of the IRS Exempt Organizations division, who may bring more knowledge of what the IRS did than the other officials the committees have chosen to interview publicly.

A report by the Treasury Inspector General for Tax Administration issued last week found the IRS had singled out conservative groups applying for tax-exempt status and subjected them to unusually intrusive questioning.

Although the hearings will provide lawmakers an opportunity to express their anger and make headlines, there may be more substantial developments behind the scenes.

On Monday, Senate Finance Chairman Max Baucus, D-Mont., and the top Finance Republican, Orrin G. Hatch of Utah, sent the IRS a list of 41 questions, covering every aspect of the controversy, that they said needed to be answered in writing by the end of the month.

“Targeting applicants for tax-exempt status using political labels threatens to undermine the public’s trust in the IRS,” the senators wrote. “Lack of candor in advising the Senate of this practice is equally troubling.”

Perhaps the most uncomfortable of the many questions that current and former IRS officials will face will be whether they misled or lied to Congress — a criminal act that is punishable by up to five years in jail.

Lawmakers are looking into several different occasions when IRS officials, including Miller and Shulman, were asked about complaints from conservative groups and answers that offered less than forthcoming answers. Confronted with earlier testimony on May 17, Miller said he had truthfully “answered questions as they were asked of me.”

That drew withering criticism from lawmakers.

“The law governing how you must respond to congressional inquiries requires you to tell not only the truth, but to tell the whole truth,” Rep. Paul D. Ryan, R-Wis., said at the Ways and Means hearing.

What the IRS did was wrong, Miller said, but it did not “target” conservative groups because it was never motivated by political concerns, only a desire to process applications more quickly and efficiently.

Adding to the frustration of lawmakers was the fact that Lerner acknowledged IRS mistakes at a tax conference on May 10 in response to a planted question, rather than first contact members of Congress who had been trying to get answers from the agency for years.

As the Justice Department conducts its own investigation into the IRS controversy, IRS officials have reason to choose their words carefully.

Laws against misleading Congress are “sweeping,” said Daniel Richman, a former federal prosecutor who teaches at Columbia University Law School.

Still, “professional prosecutors know they have to exercise real care and judgment in venturing into the area,” Richman said. “It can easily get out of hand with criminal cases being used or perceived as tools of the political process.”

Attorney General Eric H. Holder Jr. said last week that the Justice Department would take “a dispassionate view” of the IRS case.

“Anyone who has broken the law will be held accountable,” he said.

White House spokesman Jay Carney said Monday that President Barack Obama’s chief of staff, Denis McDonough, learned about the audit in advance in late April but did not tell the president about it because there was nothing to be done at that point.

Steven T. Dennis contributed to this report.