Investigators suspect that the information was fabricated to back the party's allegations that Moon's son Joon-yong landed a job at a public agency in late 2006 thanks to his father's influence.

Moon was then a senior presidential secretary.

Kim faces the charges of announcing disinformation just four days before the presidential vote.

"(I) again apologize for failing to verify whether the tipoff had been concocted, though we did our best during the verification process," Kim told a throng of reporters as he appeared at the prosecution's office.

The questioning came a day after Lee Yoo-mi, the party member accused of creating the fake tipoff, was indicted on charges of violating the Public Official Election Act.

During the meeting with reporters, Kim repeated the party's stance that Lee acted alone, and that no senior party members were implicated in the scandal.

On Wednesday, Ahn Cheol-soo, the party's former presidential candidate, apologized that the party had failed to properly verify the authenticity of the allegations against Moon's son. He said he would take "political and moral" responsibility, but apparently denied his involvement. (Yonhap)