Prosecutors summoned a presidential aide from the former Moon Jae-in administration in their investigation into the appointment of a lawmaker as head of a state agency, allegedly in exchange for hiring Moon's then-son-in-law.

The Jeonju District Prosecutors' Office on Friday began questioning former senior presidential secretary for personnel affairs Cho Hyun-ock as a witness regarding the appointment of former main opposition Democratic Party(DP) Rep. Lee Sang-jik as president of the Korea SMEs and Startups Agency in 2018.

Cho, one of the inaugural members of the Moon administration, is standing trial for the "blacklist scandal," in which the Moon government allegedly forced heads of state agencies appointed under the Park Geun-hye administration to step down between 2017 and 2018.

The prosecution suspects that Lee, founder of low-cost carrier Eastar Jet, hired Moon's then-son-in-law, identified by his surname Suh, as an executive at Thai Eastar Jet, in return for his appointment at the state agency. The Thai low-cost carrier is suspected of being under Lee's ownership.

The investigative agency is reportedly focusing on allegations that Lee had hired Suh, who lacked on-site experience in the aviation industry, despite declining performance in the industry.