Two opposition lawmakers quit a parliamentary investigative committee Wednesday in a move aimed at breaking an impasse in a probe into allegations that the state spy agency meddled in last year's presidential election.

The investigation, which began early this month for a 45-day run, has been in limbo while the rival parties have wrangled over who should represent each side on the committee.

The probe aims to uncover the truth behind allegations that former National Intelligence Service (NIS) chief Won Sei-hoon ordered an online smear campaign to sway public opinion in favor of the ruling Saenuri Party ahead of last year's Dec. 19 presidential election.

The ruling party has claimed that main opposition Democratic Party lawmakers Kim Hyun and Jin Sun-mee are unfit to carry out the probe because they are subjects of the investigation.

Kim and Jin have been accused of harassing an NIS employee suspected of posting political comments online as part of the smear campaign against the then opposition presidential candidate Moon Jae-in.

The alleged harassment is also a subject of the parliamentary investigation.

"I am resigning purely out of my sincere wish for the investigation to go smoothly despite the Saenuri Party's attempts to drag it down," Kim said in a joint press conference with Jin at the National Assembly. "This is a decision we made solely for our country."

"This will be the last time we soothe the Saenuri Party's whining with candy," Jin added. (Yonhap News)