Park Joo-sun, the interim leader of the minor opposition People's Party, stepped in to defuse an escalating feud over its former presidential candidate's leadership bid on Friday, warning that disunity could derail reform efforts.

On Thursday, Ahn Cheol-soo expressed his intention to run in the party election slated for Aug. 27, triggering criticism from his rivals who demand the new leader be one that is completely free from responsibility for the humiliating defeat in the May presidential election and a crippling fake tip-off scandal.

The announcement was made only three days after he pledged to take all "political and moral responsibility" for the scandal and take a period of "deep self-reflection." On Monday, the prosecution cleared him of any involvement.

"We have to prepare for the leadership election with the objective of party innovation based on cohesion and unity, and I hope we will refrain from engaging in excessive debate over a particular person's run in the race," Park said during a meeting of the party's interim leadership.

Announcing his decision to join the election, Ahn stressed his "sense of urgency" to salvage the party that he, along with his followers, founded with a rallying cry -- "new, clean politics" -- early last year.

But his bid was met with intense resistance.

A dozen party lawmakers issued a joint statement that urged him to deliver on his earlier pledge to reflect and stay away from party affairs for the time being. Some party members, who were closely affiliated with former President Kim Dae-jung, even threatened to leave the party.

Amid a deepening schism, concerns have risen that the party's efforts to shore up public support and carry out sweeping reform -- the key task for the new leader -- could flounder.

Since the scandal erupted in late June, the party has seen its popularity tumbling to its lowest point since its foundation. In the latest Gallup Korea survey released Friday, it scored only 5 percent, 1 percentage point lower than that of the smallest Justice Party.

The scandal revolves around a rank-and-file member accused of fabricating an election-season allegation that President Moon Jae-in's son landed a full-time job at a public agency in late 2006 thanks to his father, then a senior presidential secretary.

The party's top post has been vacant since former leader Park Jie-won resigned in May to take responsibility for the defeat in the presidential election. The new leader's term is to last until early 2019.

Four-term lawmaker Chung Dong-young and former co-chair Chun Jung-bae have already announced their election bids. Two-term lawmaker Lee Un-ju and Moon Byeong-ho, a former member of the party's Supreme Council, are also seen as potential candidates.

The two-day candidate registration for the leadership contest is set to begin next Thursday. (Yonhap)