Jeff Neely appeared before the House Committee on Oversight and Government Reform, which is investigating not only the conference but why the GSA took 11 months to alert the White House and why a bonus for Neely was approved, The Washington Post reported.
Panel Chairman Darrell Issa, R-Calif., said Neely, 57, had declined to testify.
Lawmakers voiced outrage over the lavish spending, which included $6,325 on commemorative coins, $3,200 for a mind reader and parties, with Issa saying it "should give pause to anyone who has opposed cutting government size and spending" and ranking Democrat Elijah Cummings of Maryland calling the situation "indefensible."
Former GSA administrator Martha Johnson called the scandal galling.
"I personally apologize to the American people for this entire situation," Johnson said. "As the head of the agency, I am responsible. I deeply regret that the exceedingly good work of GSA has been besmirched. I will mourn for the rest of my life the loss of my appointment."
Neely had told investigators he didn't think he needed to seek competitive bids for the conference because he was interested in quality when he planned the convention, the Post reported.
Critics say Neely, who coordinated the Western Regions conference for the GSA's Public Buildings Service, and his assistants went too far and made questionable expenditures of taxpayer dollars, the Post said.
Interviews of Neely and other GSA officials prompted GSA Inspector General Brian Miller to issue a highly critical report earlier this month about the conference. Miller last week also asked the Justice Department to investigate contract improprieties and other matters emanating from the conference for 300 employees at the M Resort Spa Casino. Miller also asked that Neely be investigated for personal use of items that were meant to be used under an employee reward program.
The scandal prompted Johnson's resignation and the firing of her two top deputies. In addition, five regional commissioners, including Neely, were placed on administrative leave pending further disciplinary action.
Celebrity Couples of 2014 [PHOTOS]