The discord between parties escalated Friday as the ruling party leader refused to apologize for derisively commenting on a minor opposition party's denial of its leaders' involvement in a fake tip-off scandal.

The opposition People's Party has demanded Choo Mi-ae, the head of the ruling Democratic Party, apologize and resign over her remarks that played down its internal probe into an alleged fabrication of misinformation about President Moon's son.

Choo ignored its demand Friday and went further saying the party should be liable for its "willful negligence" and bear the responsibility for the crisis that has thrust the party into its worst state.

"Criminal liability due to willful misconduct must be investigated, and those involved be held accountable. ... If (the party) had conviction, it would have taken actions," she said at the ruling party's Supreme Council meeting in Cheonan, south of Seoul, in the morning.

The People's Party is embroiled in a scandal involving its party members who are accused of concocting an anonymous tip-off about an unfair hiring of Moon Joon-yong by a public agency in 2006. The party used the revelation against Moon in the May presidential election.

The party has said its in-house probe found no evidence implicating its leaders, including Moon's former presidential rival Ahn Cheol-soo in connection to the alleged scheme.

Choo lashed out at the probe result Thursday, saying that the party's leadership couldn't have not known about the fabrication.

In protest, the People's Party declared a boycott of all parliamentary proceedings later.

Park Joo-sun, the interim leader of the People's Party, again stressed earlier in the day that the parliament won't be normalized unless Choo retracts her words and apologizes. 

"We won't join when we've been ridiculed and become a laughing stock," he said.

The boycott will hinder the ruling party in passing an 11.2 trillion-won ($9.69 billion) extra budget and other key bills.

The People's Party with 40 lawmakers can exercise a casting vote in key legislative affairs for the ruling party that has 120 seats in the 299-member National Assembly.

Later in the day, Assembly Speaker Chung Sye-kyun exercised his authority to refer the budget bill to the parliamentary budget committee as opposition parties had rejected lower-level committee deliberations for a month.

The budget committee is set to convene on Monday to discuss whether to table the bill. A fifth of the 50 committee members must agree for the bill's submission, but a sub-committee review to fine-tune the bill requires consent from a majority. Only 20 of the total members are from the ruling party. (Yonhap)