South Korea’s main opposition party has submitted a motion to impeach the country’s acting leader over his reluctance to fill three Constitutional Court vacancies ahead of the court’s review of rebellion charges against impeached President Yoon Suk Yeol stemming from his short-lived martial law decree on December 3.

The court appointments have stalled amid an intensifying dispute between the liberal opposition and Mr Yoon’s conservative party, and the potential impeachment of Prime Minister Han Duck-soo may deepen the political paralysis that has halted high-level diplomacy and rattled financial markets.

The opposition-controlled National Assembly also passed motions calling for the appointment of three Constitutional Court justices as the court prepares to start deliberations on whether to dismiss or reinstate Mr Yoon.

The vote came shortly after Mr Han reiterated in a televised statement that he would not appoint the justices without bipartisan consent.

National Assembly Speaker Woo Won Shik urged Mr Han to swiftly appoint the justices, saying that his calls for bipartisan consent essentially amount to a refusal and “infringes on the National Assembly’s right to select Constitutional Court justices”.

Mr Yoon’s People Power Party, whose members mostly boycotted the National Assembly vote, argued that Mr Han should not exercise presidential authority to appoint the proposed justices while Mr Yoon has yet to be formally removed from office.

The main opposition Democratic Party has accused the conservatives of undermining the court process to save Mr Yoon’s presidency, and its motion to impeach Mr Han could go to a floor vote as early as Friday.

The Democrats’ floor leader, Park Chan-dae, said Mr Han’s comments show “he lacks both the qualifications to serve as the acting leader and the will to uphold the Constitution”.

South Korean acting president Han Duck-soo has said he will not appoint the Constitutional court justices without bipartisan consent (Choi Jae-koo/Yonhap/AP)

Mr Yoon’s presidential powers were suspended after the National Assembly voted to impeach him on December 14 over an attempted power grab which lasted only hours but has triggered weeks of political turmoil that has shaken one of Asia’s most robust democracies.

To formally end Mr Yoon’s presidency, at least six justices on the nine-member Constitutional Court must vote in favour. Three seats remain vacant following retirements and a full bench could make conviction more likely.

The court, which is to hold a pre-trial hearing in Mr Yoon’s case on Friday, has said it believes the acting president can exercise the right to appoint justices.

Three of the court’s nine justices are directly appointed by the president. Three are nominated by the head of the Supreme Court and three by the National Assembly, and they are then formally appointed by the president in what is widely considered a procedural matter.

The three seats that are currently open are to be nominated by politicians.

South Korea’s Constitution states that the National Assembly “selects” three roles in the court rather than recommends, suggesting the presidential appointments for these roles are a formality rather than a substantive authority, according to some legal experts.

Mr Han said: “The consistent spirit reflected in our Constitution and laws is that an acting president should focus on maintaining stability in governance to help the country overcome crisis while refraining from exercising significant powers exclusive to the president, including appointments to constitutional institutions.

“I will withhold the appointment of Constitutional Court justices until the ruling and opposition parties submit an agreed-upon proposal.”

Mr Han has also clashed with the Democrats over his vetoes of Bills calling for independent investigations of Mr Yoon and corruption allegations involving his wife, Kim Keon Hee.

If Mr Han is impeached, Choi Sang-mok, the country’s deputy prime minister and finance minister, is next in line.

The impeachment vote against Mr Han could face legal ambiguities.

Most South Korean officials can be impeached with a simple majority of the National Assembly, but impeaching presidents requires two-thirds. The rival parties differ on which standard should apply to an acting president.

The Democratic Party controls 170 of the National Assembly’s 300 seats, so it would need support from members of other parties including Mr Yoon’s own to get a two-thirds majority.

While focusing on defending himself in the Constitutional Court, Mr Yoon has dodged several requests by law enforcement authorities to appear for questioning over rebellion charges and also blocked searches of his office.

Authorities have already arrested Mr Yoon’s defence minister, police chief and several other military commanders involved in the attempt to implement martial law, which harkened back to the days of authoritarian leaders the country hasn’t seen since the 1980s.

In a news conference in Seoul, Yoo Seung Soo, lawyer for former defence minister Kim Yong Hyun, repeated Mr Yoon’s claim that his martial law decree was to “sound the alarm against … political abuse” by an opposition that has bogged down his agenda, and did not amount to a rebellion.