The chairman of the congressional committee holding the first hearing on a federal agency's now-infamous Las Vegas conference complained Monday that the organizer behind the spending spree -- who is also one of his key witnesses -- is still being paid. 

Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, noted that Jeffrey Neely is on administrative leave along with four other employees of the General Services Administration. 

Neely is expected to invoke his Fifth Amendment right not to answer questions during testimony at the hearing set for Monday afternoon. 

Issa told Fox News that while the hearing will be about broader issues of spending and accountability at the agency, he hopes Neely gets booted off the payroll. 

"Remember, this is an individual who's still being paid today by the American people," Issa said. "He hasn't been fired." 

Two GSA officials were fired after an inspector general report found the agency spent more than $820,000 on the 2010 conference. The head of GSA also resigned. 

Neely, on leave as regional commissioner of the Public Buildings Service for the Pacific Rim, was largely responsible for the Las Vegas conference. 

The Oversight Committees released internal memos that showed GSA officials debated last year whether to give Neely a bonus for his job performance. The officials were aware at the time that the inspector general was investigating the conference spending. 

The now-resigned GSA administrator, Martha Johnson, granted Neely a $9,000 bonus over the objection of Deputy Administrator Susan Brita. 

Brita wrote in a November 2011 email, that "based on what we know already" about the conference and a questionable awards program, "I would not recommend a bonus." 

Johnson wrote in an email, "yes on a bonus" in part because Neely had to serve in an acting capacity "forever and a day." 

Lawmakers at this point are looking beyond the 2010 conference itself and into other areas where the agency may have spent money imprudently, such as on employee incentive programs. 

The hearing Monday will surely fuel the controversy, which has expanded almost daily as new details emerge about the decision-making at the top levels of the GSA. 

Issa said the conference is the "tip of the iceberg." 

"Although (Neely) may soon be leaving the GSA, we hope, we want to know when he's out the door how we're going to change behavior throughout the government service," Issa said Monday. 

Among those on the witness list Monday are GSA Inspector General Brian Miller and Johnson. 

The Associated Press contributed to this report.