State prosecutors are set to launch an investigation this week into allegations that the National Intelligence Service blacklisted media professionals deemed unfriendly to the Lee Myung-bak administration, sources said Sunday. 

The Seoul Central District Prosecutors’ Office, which is looking into the NIS over its involvement in blacklisting left-wing figures under the Lee administration, is reported to be planning to question individuals on the list starting this week.

During the Lee administration, which ended in 2013, the NIS allegedly pressured public broadcasting companies to send out biased information in support of conservatives under the leadership of former NIS chief Won Sei-hoon.

Won was recently sentenced to four years in prison for his role in the agency’s covert cyber operation aimed to bolster the political base of conservatives and to support former President Park Geun-hye’s election campaign.

The NIS Reform Committee -- a body launched by President Moon Jae-in to tackle irregularities committed under the Lee and Park administrations -- has also claimed that the spy agency engaged in a smear campaign on social media against left-wing Seoul Mayor Park Won-soon in the 2011 mayoral election.

Seoul Mayor Park filed a complaint last week against Lee, saying that the former president masterminded the NIS’ political interference and the spy agency’s role in creating the blacklist. Regarding the complaint, prosecutors are expected to summon Won -- and possibly Lee -- to question them over the scandal.

The NIS internal task force also found that its former chief Won allegedly headed the spy agency’s compilation of a blacklist of reporters, producers, artists and cultural figures critical of the government and peddled influence in human resources.

The blacklist came to light in the wake of an investigation into the corruption scandal that led to the ouster of former President Park.

Amid the scandal, labor unions of Korean Broadcasting Service and Munhwa Broadcasting Co. are taking their own action, calling for the CEOs of the two companies, who are accused of colluding with the NIS to discriminate against dissenting employees, to step down.

By Bak Se-hwan (sh@heraldcorp.com)