Independent lawmaker Ahn Cheol-soo called for bipartisan support on Monday to launch a special investigation into several government bodies and the military embroiled in an online campaign scandal in connection with last year's presidential election.

"I think a comprehensive investigation by an independent counsel can clear up the allegations," Ahn said in a press briefing held at the National Assembly. "I doubt the ongoing probes separately conducted by state prosecutors and military prosecutors can get to the bottom of the scandal."

Ahn questioned the credibility of the ongoing probe, citing discord between the justice ministry and state prosecutors over the scope of the investigation and procedural issues.

"I wonder if the government truly has the willingness to investigate this case," Ahn said. "Under these circumstances, I doubt whether people would trust the investigation results by prosecutors."

Ahn, who withdrew his presidential candidacy before the Dec. 19 vote to back the main opposition candidate, strongly criticized political parties' wrangling over the election meddling scandal, which originated from the National Intelligence Service (NIS) and has spilled over to the defense ministry's Cyber Warfare Command and other government agencies.

Former NIS chief Won Sei-hoon is currently undergoing trials on charges of illegal electioneering, while a team of military prosecutors is investigating similar allegations involving cyber command officials who posted online comments against then opposition candidate Moon Jae-in, who subsequently lost to then ruling party candidate Park Geun-hye.

During the recent parliamentary audit, opposition lawmakers raised allegations that several other government agencies also conducted an online smear campaign ahead of the vote, calling for probes.

Ahn's latest move comes at a time when the 51-year-old former entrepreneur is gathering supporters to establish a new political party, a move that could pose serious challenge to the main opposition Democratic Party (DP) as Ahn wields significant sway over the liberal voting bloc.

It also comes after President Park ordered thorough investigation to clear up the allegations, denying any link to the snowballing scandal.

Ahn, the founder of South Korea's largest anti-virus software firm AhnLab Inc., had entered last year's presidential campaign with huge support from young liberal voters despite having no prior experience in politics, painting himself as an outsider untainted by party politics.

He later dropped out of the race to back opposition candidate Moon. Ahn was later elected to parliament in April's by-election, becoming a first-term lawmaker. 

The ruling Saenuri Party expressed opposition to Ahn's demand, claiming such a move could undermine the division of powers between the administrative and legislative branches.

"Launching a special probe with parliamentary approval goes against the principle of division of powers, because prosecutors are currently looking into the case according to established legal procedure," floor spokesman Kim Tae-heum said in a briefing.

Kim criticized the novice lawmaker for trying to raise his political profile through the case, urging him to leave the ongoing investigation in the hands of prosecutors.

The DP took a cautious stance on the time-consuming process that would require consent from the ruling party, which holds a majority in the parliament.

"The DP basically agrees with Ahn in that the political circle should focus more on people's livelihoods by wrapping up investigations into government agencies' election meddling," DP spokesman Kim Kwan-young said.

"However, the decision on the special probe should be made by taking all things into consideration, including the ongoing prosecution's investigations, trials and probes into allegations involving other government agencies."

To launch a special investigation into a high-profile case, a bill should pass through the National Assembly. Upon the bill's passage, President Park should designate a special prosecutor tasked with leading the investigation within an agreed-upon time frame. (Yonhap News)