By Jack Kim
SEOUL (Reuters) -South Korea's main opposition party introduced a bill to impeach acting President Han Duck-soo on Thursday, a day before it plans to seek a vote on the move, which could deepen a constitutional crisis triggered by a short-lived martial law.
The opposition Democratic Party had threatened to impeach Han if he did not immediately appoint three justices to fill the vacancies at the Constitutional Court. Parliament backed three nominees on Thursday, but Han has yet to formally appoint them.
The court is trying the impeachment of President Yoon Suk Yeol over his Dec. 3 declaration of martial law.
"It has become clear that Prime Minister and acting President Han Duck-soo does not have the qualification or the will to safeguard the Constitution," Democratic Party floor leader Park Chan-dae said in a statement.
The impeachment motion, which must be voted on within 24 to 72 hours, cited a range of actions by Han as grounds for his impeachment, including his veto of a special prosecutor bill to investigate alleged wrongdoings by the first lady.
If Han is impeached, the finance minister will assume the acting presidency.
The Democratic Party has majority control of parliament, but there is disagreement between the parties and some constitutional scholars over whether a simple majority or a two-thirds vote is needed to impeach the acting president.
The interim leader of Yoon's ruling party, Kwon Young-se, told reporters impeaching Han would be a mistake that would drive the economy into a "major crisis" possibly by triggering a financial crisis, the Yonhap news agency said.
Earlier on Thursday, Han said that he would not appoint the justices until political parties agreed on the appointments, saying it would harm constitutional order for him do it without such a consensus.
Two of the proposed court appointees approved on Thursday were nominated by the Democratic Party and one by Han's ruling People Power Party. The ruling party objected to that breakdown of candidates, saying it had not agreed to it.
Han has been under pressure to make the appointments, but political parties have disagreed on whether he has the authority to do so as acting president.
The court is set to hold its first hearing on Friday in the trial to decide whether to remove Yoon or reinstate him.
Under the constitution, six justices must agree to remove an impeached president, meaning the current justices must vote unanimously to remove Yoon. The court has said it can deliberate without the full nine-member bench.
Yoon, who was impeached by parliament on Dec. 14 in a vote joined by some members of his centre-right party, has not met a court request to submit legal papers as of Thursday, its spokesperson, Lee Jean, told a media briefing.
On Wednesday, he did not respond to the latest summons for questioning in a separate criminal investigation. Investigators sent him another summons on Thursday to appear on Dec. 29.
Yoon's repeated defiance has sparked criticism and calls from the opposition for his arrest.
Earlier on Thursday, lawyers for Yoon's former defence minister, who is being investigated on insurrection charges over the martial law declaration, said it was intended to raise alarm at opposition parties' abuse of the democratic process.
Kim Yong-hyun, the first official arrested, is likely to be the first to face an indictment of being a central figure in Yoon's surprise declaration of martial law.