The Seoul Central District Prosecutors' Office is expected to investigate the nature of a five-billion-won severance pay the son of a lawmaker received from a company at the center of a scandal involving a highly lucrative development project.

Since the report emerged on Sunday, Rep. Kwak Sang-do has left the main opposition People Power Party(PPP).

The son and the company insist the payment was fair, but controversy continues due to the large amount. Bribery speculations have been raised by the ruling camp.

Prosecutors will likely look into what kind of job the son was tasked with at the asset management firm Hwacheon Daeyu and whether other employees claimed a similar sum.

The 32-year-old reportedly joined the firm in June 2015 and was paid two-point-three to three-point-eight million won in monthly wages. He left this March with a handsome payment of two-point-eight billion won after taxes that included consolation, performance and severance pay.

The son explained he was unable to work any longer due to health reasons. The company acknowledged that excessive workload played a role in his poor health, for which he was compensated.

Hwacheon Daeyu is accused of receiving favors in a development project in Seongnam City when Gyeonggi Province Gov. Lee Jae-myung was mayor of the city.