Ahn Cheol-soo, former presidential candidate of the opposition People's Party, on Wednesday apologised for the scandal revolving around fabricated smear campaign against President Moon Jae-in.
"(Fabricating information) cannot be countenanced under any circumstance. I was shocked when I was first informed, and feel responsible as the presidential candidate of the People's Party," Ahn said.
"I bow in apology to the people who supported me, and to the party members and fellow politicians. I also apologise to those involved who would have felt emotional pain."
Ahn also called on the People's Party to co-operate with the investigations, and that all responsibility lies with him.
"The political and moral responsibility is with me. I will lay down everything, and look back at the past five years I lived as a politician," Ahn said, going on to say that the People's Party will do everything possible to regain the trust of the people.
Ahn's statement comes after a former senior party member was arrested over his alleged involvement in the plot, feeding speculation that the investigation will move on to those higher up the party.
In the early hours of Wednesday, the Seoul Central District Court approved the arrest of Lee Jun-seo, acknowledging the prosecution's claims that there was a risk that Lee may flee or destroy evidence.
Lee was a member of the party's supreme council, and is accused of providing the party with the unsubstantiated allegation that President Moon Jae-in's son, Moon Joon-yong was hired unfairly by a public agency in 2006. The information formed the basis of an unsuccessful smear campaign by the party against Moon.
The information has since been revealed to have been fabricated by Lee You-mi, a former campaigner for Ahn. Lee You-mi, who is currently under arrest, confessed that she had her brother pose as a friend of Moon Joon-yong to create the recording in which the accusation is made.
The recording was then passed on to Lee Jun-seo via a mobile messenger.
While it remains unclear whether Lee You-mi was working under orders from Lee Jun-seo, it has been alleged that he promised her a position in the party in exchange for her providing "decisive proof" in the younger Moon's hiring process.
Lee Jun-seo is also said to have told the party leadership that the information was true, despite being aware that it was produced by Lee You-mi and her brother.
The People's Party, whose own probe concluded that Lee You-mi had acted on her own initiative, has accused the prosecution of bias, and has called for an independent counsel investigation.