WASHINGTON — The Internal Revenue Service spent $4.1 million on a single conference in Southern California in 2010, paying top dollar for luxury suites, $27,500 for a keynote speaker and tens of thousands of dollars for gifts to the 2,600 people who attended, according to a newly released Treasury Department audit.

But the audit also shows that such expenditures fell dramatically when the Obama White House clamped down on travel and conferences as budgets tightened and a scandal erupted over how much the General Services Administration had spent on conferences. I.R.S. spending on such meetings fell to $4.8 million in the 2012 fiscal year, which ended Sept. 30, from $37.5 million in fiscal 2010.

The audit, conducted by the Treasury inspector general for tax administration, has given Republicans a new reason to be outraged at the nation’s tax-collecting agency, which is already under fire for targeting conservative groups for special scrutiny when applying for tax-exempt status.

The House Ways and Means Committee opened hearings on Tuesday to take testimony from members of the Tea Party and other conservative groups that say they were mistreated by the I.R.S.

“Today’s witnesses will help this committee and the American people better understand just how far off track the I.R.S. has gone,” said Representative Dave Camp of Michigan, the committee chairman. “Victims included Tea Party and non-Tea Party groups, 501(c)(4) social welfare organizations and 501(c)(3) charitable organizations, including religious organizations. All of the witnesses received onerous and intrusive questionnaires from I.R.S. agents across the country. Some even had their confidential information leaked by the I.R.S. to the media, which can have the impact of chilling free speech.”

But the inspector general’s audit on excessive conference spending also bolstered White House claims that it has reined in such spending since the G.S.A.’s lavish expenditures came to light in the spring of 2012. The audit focused on a single conference of the I.R.S. Small Business/Self-Employed Division in August 2010. It was the most expensive conference from 2010 to 2012, the period examined.

Click here for the full story.