The report by Treasury Department's inspector general, set to be released Tuesday, comes as the IRS already is facing bipartisan criticism after agency officials disclosed they had targeted tea party and other conservative groups seeking tax-exempt status to extra scrutiny.
Agency officials and the Obama administration have said that treatment was inappropriate. But the political tempest is showing no signs of ebbing and has put the White House on the defensive. Three congressional committees are investigating and a Justice Department criminal investigation is underway, and President Barack Obama has replaced the IRS's acting commissioner while two other top officials have stepped aside.
On Friday, the new acting commissioner, Danny Werfel, released a statement on the forthcoming report criticizing the Anaheim meeting.
"This conference is an unfortunate vestige from a prior era," Werfel said. "While there were legitimate reasons for holding the meeting, many of the expenses associated with it were inappropriate and should not have occurred."
Werfel, a former official at the White House Office of Management and Budget, said reducing excessive personal travel has been "a personal priority for me" and that "taxpayers should take comfort that a conference like this would not take place today."
The report will be the subject of a hearing Thursday by the House Oversight and Government Reform Committee.
Werfel is scheduled to make his first congressional appearance as acting commissioner Monday when he appears Monday before a subcommittee of the House Appropriations Committee.
According to congressional aides briefed by the inspector general's office, the IRS also did not formally seek competitive bids for the city where the agency's 2010 conference was held, for the event planner who assisted the agency, or for the speakers.
The aides, who spoke on condition of anonymity to describe a confidential congressional briefing, said other benefits given to some attendees at the Anaheim IRS conference included vouchers for free drinks and some tickets to attend Angels baseball games.
"So they end up with free drinks, they ended up with tickets to games, basically kickbacks," the committee chairman, Rep. Darrell Issa, R-Calif., said Sunday on CNN's "State of the Union."
Two videos produced by the IRS were shown at the Anaheim conference. In one, agency employees did a parody of "Star Trek" while dressed like the TV show's characters; the second shows more than a dozen IRS workers dancing on a stage. The two cost the agency more than $50,000 to make, aides said.
The lecturer who spoke about art through leadership produced six paintings while speaking, with subjects that included Abraham Lincoln, Michael Jordan, the rock singer Bono and the Statue of Liberty, the aides said.