An existing fissure within the main opposition party is projected to widen ahead of the April general election, with several current and former heavyweight members parting ways from the party.

Former leader of the Democratic Party of Korea and ex-Prime Minister Lee Nak-yon said Monday that he would officially announce his departure from the main opposition party through a press conference at the National Assembly scheduled for Thursday.

The former premier had hinted on Sunday that the announcement could come later in the week, breaking an almost weeklong silence on the matter. He had refrained from discussing the issue in public in apparent respect for party leader Lee Jae-myung as he recovers from surgery following a knife attack on Jan. 2.

“I need to discuss some matters with my fellow (politicians), but I’m expecting to say goodbye and ask for forgiveness in the latter half of this week,” Lee Nak-yon said while on a visit to the southern city of Gwangju to pay respects to the victims of the 1980 Democratic Uprising.

The ex-prime minister last year announced he would quit the main opposition party to establish a new political party of his own. He has openly criticized Lee Jae-myung’s monopoly of power within the party.

Lee Nak-yon’s planned departure is projected to deal a heavy blow to the party in the upcoming election, with several political bigwigs having expressed interest in joining the new party.

“At least seven or eight incumbent lawmakers are interested in joining Lee Nak-yon’s new party,” former National Assembly Deputy Speaker and Democratic Party Rep. Lee Seok-hyun said in a Monday radio interview. The former deputy Assembly speaker himself recently revealed his plans to leave and join the prime minister.

Another politician who has turned his back on the Democratic Party is five-term lawmaker Lee Sang-min. He officially joined the rival People Power Party on Monday, a month after leaving the main opposition in early December.

“With the ruling party as a minority and the opposition taking up the majority in the Assembly, there has been too much noise in the state of affairs,” the five-term lawmaker said in a welcoming event hosted by the People Power Party at the National Assembly.

“The Democratic Party is now merely a shield for Lee Jae-myung, who has made the group his private party,” he added.

Democratic Party Reps. Kim Jong-min, Yoon Young-chan, Lee Won-wook and Cho Eung-cheon -- four members outside the party's mainstream known collectively as the group “Principles and Common Sense” -- are also gearing up to leave. They have announced their plans to quit the party if Lee Jae-myung refuses to step down from his current leadership position. Lee is expected to keep his role as chairman after having already refused a similar request from Lee Nak-yon last month.

A Seoul Court on Monday also rejected an injunction filed by main opposition party members to suspend Lee Jae-myung from his current chairmanship. They filed the injunction with the Seoul Southern District Court in October, accusing Lee of breaches of trust, bribery and other charges. Prosecutors have accused Lee of committing such crimes during his time as the mayor of Seongnam, Gyeonggi Province, from 2014-2018 in connection with a scandal-ridden land development project in the city's Bundang district.

The moves and announcements of departures come as the Democratic Party has been dealing with an unexpected leadership void following Lee Jae-myung’s hospitalization after he was stabbed in the neck in Busan.

The stabbing occurred just 100 days before the April 10 general election, as rival parties have engaged in a tug-of-war for the National Assembly.