Opposition lawmakers in South Korea have filed a motion to impeach Prime Minister and acting leader Han Dak-soo, less than two weeks after parliament voted to impeach President Yoon Suk-yeol.
It comes after Khan refused to appoint constitutional court judges nominated by the main opposition Democratic Party (DP).
“Han has revealed that he is an acting rebel, not an acting president,” DP leader Park Chan-dae said on Thursday.
The opposition also accused Khan of aiding Yun's attempt to impose martial law on December 3. Khan had earlier apologized for not being able to block it.
Khan also vetoed several opposition-led bills, including one that proposed a special investigation into Yun's short-lived declaration of martial law.
The impeachment motion is expected to be voted on in the next 24 to 72 hours.
In order to succeed, 151 out of 300 deputies must vote for him.
The DP currently holds 170 of the 300 seats in the parliament. The opposition bloc together has 192 seats.
Opposition parties had hoped that Khan would not interfere while acting as the country's interim president and that he would allow bills to pass.
But instead he stood firm, deepening political infighting.
On Tuesday, Khan closed a cabinet meeting without revising two opposition-sponsored bills that called for special investigations into the declaration of martial law and corruption allegations involving first lady Kim Keon-hee.
He said he did not include them on the agenda to give more time to the ruling party and the opposition to reach a compromise.
But DP group leader Park Chan-dae criticized him for “buying time and prolonging the rebellion”.
“We have clearly warned that it is entirely up to Prime Minister Han Duk-soo whether he will go down in history as a disgraced figure, as a puppet of the leader of the rebel conspiracy Yoon Suk-yeol, or a civil servant who faithfully followed the orders of the public,” Park said on televised party meeting.
And on Thursday, Khan said he would not appoint the three judges nominated by the opposition-dominated National Assembly to the constitutional court – which is debating whether Yun should be removed from office – unless the rival parties reach a consensus.
To that, Park said that “it has become clear that Han Duk-soo is neither qualified nor willing to defend the constitution,” adding that the opposition would “immediately” introduce the impeachment bill.
Khan's ruling People's Power Party said the opposition's threats had interfered with Khan's “legitimate exercise of power”, while a senior official in the Prime Minister's Office criticized the threats as “extremely regrettable”.
Han stepped in as interim president after Yoon was ousted earlier this month. If lawmakers vote to impeach Khan, Finance Minister Choi Sang-mok will be next in line.
This latest development in the country's political turmoil comes as Seoul's Constitutional Court debates whether Yun should be permanently removed from office.
The court is expected to hold its first public hearing later this week.
It is unclear whether Yoon himself will take the stand during the hearings, but protesters have vowed to continue their calls for Yoon's removal during the court proceedings.
Yun is also under investigation for alleged sedition over his failed attempt to place the country under martial law.
He refused to accept several subpoenas served on him, and investigators warned they could issue a warrant for his arrest if he continued to not respond.
Several high-ranking officials – including former defense minister Kim Yong-hyun, former interior minister Lee Sang-min and army chief Park Ahn-soo – are also under investigation.
Additional reporting by Jake Kwon and Hosu Lee in Seoul