The main opposition People Power Party has called on Prime Minister nominee Kim Min-seok to withdraw his candidacy over a series of allegations.

Party floor leader Kweon Seong-dong on Monday cited Kim’s ties to a political donor, Kang Shin-sung, who was convicted of providing illegal funds, saying the two were in “political symbiosis.”

Lawmaker Kim Gi-hyeon also rejected Kim’s claim that his past convictions stemmed from a “politically motivated investigation,” calling such an attitude unfit for a prime ministerial candidate.

Rep. Joo Jin-woo raised additional concerns over allegations that Kim used his position to advance his son’s academic and professional prospects.

The opposition has demanded that Kim voluntarily step down ahead of his confirmation hearing.

Kim has denied all the allegations, insisting he was the target of a politically motivated  investigation.