Rep. Kweon Seong-dong, floor leader of the ruling People Power Party, speaks during a press conference at the National Assembly in Seoul, Sunday. Yonhap

The two main rival parties clashed on Sunday over whether acting President Choi Sang-mok should postpone the appointment of Constitutional Court justice nominee Ma Eun-hyuk, following the court's ruling on Choi choosing to delay judicial proceedings.

The appointment of Ma, as nominated by the main opposition Democratic Party of Korea (DPK), will complete the selection of Constitutional Court judges who will rule on the impeachment motion against embattled President Yoon Suk Yeol. Under the law, at least six justices must approve an impeachment for it to be upheld, meaning the appointment of an additional justice could raise the likelihood of Yoon's impeachment being upheld.

The court is set to rule on Monday as to whether Choi's delay in appointing Ma was constitutional.

This comes after the acting president appointed two of the three justice nominees recommended by the National Assembly but postponed Ma's appointment, citing a lack of consensus between the ruling People Power Party (PPP) and the DPK.

In response, the National Assembly requested a ruling on the constitutionality of Choi's decision. If the court rules that Choi's actions were unconstitutional, he will be required to appoint Ma as a Constitutional Court justice, thereby filling the nine-member bench.

PPP floor leader Rep. Kweon Seong-dong said Choi should delay Ma's appointment, even if the court rules his actions unconstitutional.

"The legal dispute has serious procedural errors. The party involved was actually Assembly Speaker Woo Won-shik himself, not the Assembly. He made a unilateral decision without following the resolution process," Kweon said during a press conference, Sunday.

"The appointment of Ma must be put on hold until Prime Minister Han Duck-soo's impeachment is confirmed by the court."

The opposition-controlled Assembly impeached Han, then acting president, on Dec. 27, a day after he vowed not to appoint three justices to the Constitutional Court. The PPP has called Han's impeachment invalid and filed an injunction with the court to suspend it.

The PPP has also raised concerns about the impartiality of justices involved in Yoon's impeachment case, specifically questioning the objectivity of Justice Moon Hyung-bae due to his past social media interactions with DPK Chairman Rep. Lee Jae-myung.

The ruling party also criticized justices Lee Mi-seon and Chung Gye-seon for their alleged ties to a progressive law research association. Yoon's legal team requested the removal of three justices from the impeachment case, raising concerns about their political impartiality.

Rep. Kim Yun-duk, secretary general of the main opposition Democratic Party of Korea, speaks during a press conference at the National Assembly in Seoul, Sunday. Yonhap

The DPK, meanwhile, called for a decisive ruling from the court on Choi's judicial delay.

"The judiciary must put a stop to Choi's attempts to destroy the Constitution," Rep. Kim Yun-duk, secretary general of the DPK, said.

He also criticized the PPP for aligning with far-right supporters and fueling hostility toward the judiciary.

"The PPP must immediately cease its efforts to undermine the judiciary and challenge its authority," Kim said.

The Constitutional Court refuted allegations surrounding the justices, saying that impeachment trials are not influenced by their personal inclinations.

"The impeachment trials only focus on whether a respondent's actions violated the Constitution or the law along with the severity of such violations," the court's press officer, Cheon Jae-hyun, said Friday. "Justices' decisions are made through an objective legal process, not based on the personal inclinations of individual judges."