Seoul –

South Korea's ruling Democratic Party said on Wednesday it was trying to regain public trust by asking 12 lawmakers to leave the party over a property scandal that has alienated voters.

The insider land trading scandal, alongside skyrocketing home prices and deepening inequality, has contributed to President Moon Jae-in's approval ratings plunging to record lows and his party's abject defeat in key mayoral elections in April.

Offering a public apology last week, Prime Minister Kim Boo-kyum said 20 people had been arrested and 529 referred to prosecutors, including 90 members of the parliament and high-level and local government officials, as part of an intra-agency investigation.

And on Tuesday, the ruling party said a state watchdog had found that 12 of its MPs or their families were suspected of unlawful property dealings, and had advised them to withdraw their membership.

Six agreed to leave saying they would return after clearing their names, while three rejected the request, claiming innocence. The other three said they will cooperate with the investigation, without elaborating.

Many South Koreans have expressed disgust over the scandal with the taunt "naeronambul," which translates to: "If I do it, it's a romance. If you do it, it's adultery."

Mounting disillusion with the government could threaten Moon's efforts to achieve policy goals, and has left the party in need of an image makeover before next year's presidential election.

Speaking on Wednesday, Democratic Party chairman Song Young-gil said the decision to ask the MPs to leave was not a disciplinary action but a step that had to be taken prior to a formal investigation, which is needed to regain public trust.

"It's an inevitable measure to relieve people's distrust over the naeronambul attitude and the property issue," he told a televised meeting. "It's heartbreaking, but a desperate attempt for change."