Ruling People Power Party leader Han Dong-hoon speaks during a press conference at the National Assembly in Seoul, Dec. 12. Yonhap

The leader of the ruling People Power Party (PPP) on Thursday threw his support behind a parliamentary vote to impeach President Yoon Suk Yeol over his failed bid to impose martial law, while calling for convening an ethics committee to discuss whether to demand Yoon leave the party.

PPP leader Han Dong-hoon made the call after Yoon defended the Dec. 3 martial law declaration as an act of governance and rejected insurrection charges against him in a public address.

"The president's duties must be swiftly straightened out and suspended through the impeachment process," Han told reporters at the National Assembly in western Seoul. "Our party must support impeachment as the party line."

Han said it has become "more clear" that Yoon is unable to carry out his duties as president, adding that his address came as a surprise.

The main opposition Democratic Party of Korea is set to file a new motion to impeach Yoon later in the day, after a parliamentary impeachment vote failed Saturday as the majority of PPP lawmakers boycotted it.

Earlier in the day, Han voiced support for Yoon's impeachment, calling on lawmakers to vote on the next impeachment motion based on their own "conviction."

"We must stop further confusion. There is only one effective method now," Han said in a press conference. "In the next (impeachment motion) vote, our party's lawmakers should enter the assembly hall and take part in the vote based on their own conviction and conscience."

Han's remarks marked a shift from his party's earlier stance to push for Yoon's "orderly" resignation. Before the Saturday impeachment vote, Yoon had vowed to leave all decisions, including his term, to the PPP.