The ruling Democratic Party decided Monday to expel two members involved in an online opinion rigging scandal amid fears that the scandal could negatively affect its preparations for the June local elections.

The party's Supreme Council also agreed to form a fact-finding panel to look into the scandal so as to "restore the honor of the party members," party officials said.

Last Friday, three DP members were detained for allegedly using a computer program to jack up the number of "like" or "feel the same way" clicks for comments critical of the government on news stories carried by the online portal Naver. 

They reportedly told police earlier that they obtained a rigging program by chance and wanted to make it look like conservatives manipulated online opinions as they tried to test the program. Among them is a blogger, surnamed Kim, who goes by an alias, "Druking."

"The Druking case is an anti-democratic act that impedes the formation of sound public opinion and threatens democracy," Choo Mi-ae, the DP chairwoman, said during a meeting with top party officials.

"The investigation authorities must definitely find the impure motives and the forces behind the opinion rigging," she added.

Choo, in addition, expressed "serious concerns" over the opposition parties' political offensive against her party.

"We will strongly respond to the political offensive that misleads the public as if the government was responsible for (the

scandal) just because Rep. Kim Kyoung-soo had had contact with (Druking)," she said.

DP lawmaker Kim, a close confidant of President Moon Jae-in, has denied any involvement in the alleged opinion rigging scam, amid a flurry of news reports suggesting his possible implication in the case.

Despite Choo's warning, the opposition parties stepped up their offensive against the ruling bloc.

"We have to clarify the suspicion over whether the Democratic Party was aware of the case or collectively carried out (the opinion rigging), and gravely punish anyone responsible," Chang Byoung-wan, the floor leader of the minor opposition Party for Democracy and Peace, said.

The Bareunmirae Party also called for a thorough probe into the case.

"Our party will verify the truth to check what kind of opinion rigging compromised democracy during last year's presidential election," Yoo Seong-min, the party's co-leader, said.

The main opposition Liberty Korea Party is expected to decide to push an independent counsel probe into the case during a general meeting of its lawmakers in the afternoon.(Yonhap)