Lee Jun-seok, an estranged former leader of the ruling People Power Party (PPP), said Sunday that he will set up a new party to push for political reform if President Yoon Suk Yeol does not change his way of doing politics by the end of this year.

Lee made the pledge during a meeting with the public, saying Yoon has not sought any changes even after the party lost to the main opposition Democratic Party (DP) in the crucial by-election for chief of Seoul's Gangseo Ward last month.

"I clearly know the path I should take and will not repeat the mistakes of the past," Lee said. "I don't think Yoon is likely to change. Without any major changes by Dec. 27, I will create a new party."

On Dec. 27, the National Assembly is supposed to vote on whether to launch special counsel probes into the Daejang-dong development scandal involving DP Leader Lee Jae-myung and suspected stock manipulation by first lady Kim Keon Hee, where Yoon can exercise the right of veto.

"I am not going to create a new party because I hate Yoon or want to get revenge on him," Lee said, stressing that he aims at "political reform."

Last month's poll was considered a key test of voter sentiment ahead of the parliamentary elections in April.

Lee has hinted at joining forces with Yoo Seong-min, a former four-term lawmaker who is known as a key critic of President Yoon Suk Yeol within the PPP.

Both ruling and opposition parties are closely watching the developments regarding the establishment of the new party and its possible effects on the April elections.

Supporters of Lee Jun-seok and Yoo say the envisioned party could potentially serve as a deciding factor in the upcoming elections, as they have a support base that the PPP currently lacks.

There is also the possibility of the new entity attracting some of the DP lawmakers who are not aligned with the party chief.

Rep. Lee Sang-min of the DP, a five-term lawmaker and one of the veteran lawmakers, has raised the possibility of joining Lee Jun-seok. (Yonhap)