A four-term lawmaker previously affiliated with the main opposition Democratic Party joined the ruling People Power Party on Monday as a factional rift in the Democratic Party deepened over candidate nominations for the April 10 parliamentary elections.

Rep. Kim Young-joo, a deputy National Assembly speaker, quit the Democratic Party last month, protesting the party's inclusion of her in a list of underperformers to be disadvantaged in election nominations amid allegations the party is sidelining those not aligned with leader Lee Jae-myung.

Non-mainstream members have claimed the list amounts to a "massacre" of those outside the pro-Lee faction.

"I believe (politics) should not be used as a tool for personal gain or selfish desires," Kim said, apparently referring to Lee.

The People Power Party is most likely to nominate Kim as its candidate for Seoul's Yeongdeungpo district, her home turf.

Kim is also reportedly set to resign from the deputy speaker position later in the day, as the seat is allocated to the Democratic Party.

Another heavyweight politician excluded from the Democratic Party nominations was Im Jong-seok, a former chief of staff for preceding President Moon Jae-in. Im had initially strongly protested his exclusion from nominations but announced Monday that he would accept the decision.

"I accept the party's decision," Im said in a Facebook post after previously urging the party leadership to reconsider its decision to exclude him.

Despite widespread speculation about defections, a close confidant of Im told Yonhap News Agency that his message should be interpreted as his intention to remain with the party.

Earlier, Im reportedly met with Lee Nak-yon, a former prime minister who had previously defected from the Democratic Party to launch a new party. Lee criticized the Democratic Party for becoming what he called party leader Lee's personal faction.

Democratic Party Chairman Lee, meanwhile, appreciated Im's decision to remain within the party, urging him to join forces to win the elections.

Despite Im's decision, the Democratic Party could potentially face more defections, including Rep. Hong Young-pyo, another four-term lawmaker who served as the Democratic Party's floor leader and is considered outside the pro-Lee faction.

Hong is also expected to announce his future plans after being categorized as one of the lower 20 percent underperformers.

He has hinted at either joining Lee Nak-yon's party or an envisioned party led by Rep. Sul Hoon, a four-term member who also announced his departure from the Democratic Party last week. (Yonhap)