An Hee-jung, a heavyweight politician and governor of South Chungcheong Province, said Tuesday he would quit after his female secretary claimed that he had sexually assaulted her several times.
An said in his Facebook account that I am going to resign from the governor and to stop all his political activities, admitting his sexual misconduct.
"It is all my fault. I seek forgiveness for my foolish act," he wrote.
An has been accused by his former female secretary of sexual assault and rape.
Kim Ji-eun appeared on a JTBC news programme on Monday evening, where she made her allegations public. She said she plans to file a legal complaint against An with the prosecution on Tuesday.
Kim alleged that An raped her four times in the course of some eight months, from June 2017 to February this year, and sexually harassed her on many occasions.
The alleged victim said she was raped by An in Switzerland and Russia, among other places, while they were on business trips together.
Kim said she decided to come forward as the governor continued abusing her in February, even after the #MeToo movement began in earnest in Korea at the end of January.
"I did not have the courage to come forward, but I was inspired by those participating in the #MeToo movement," she said.
The alleged victim said that because of the power imbalance, it was extremely hard to reject An's requests and orders while working for him. Kim said she is terrified of what will happen after the TV interview.
"The person I am most scared of is Gov. An Hee-jung," she said with her eyes tearing up during the interview.
"I thought I could just disappear any day after today. I felt like going on TV was one of the very few ways to protect myself. I hope my fellow citizens can protect me."
Kim also said there are other victims of sexual violence in Gov. An's office.
An, who worked as a political aide to the late President Roh Moo-hyun during Roh's presidential campaign in 2002, was considered the main "darkhorse" contender for the Democratic Party's presidential nomination against the then-frontrunner and South Korea's current President Moon Jae-in.
The governor is currently considered as a leading candidate for the next presidential election.
An, who is married, said he did have intercourse with Kim, but his office claimed it was consensual. But in his Facebook, the governor said his office made a wrong announcement.
On the same day Kim made her public accusation against An, the governor spoke about the #MeToo movement at a public engagement, publicly endorsing the campaign.
"I see the ongoing #MeToo movement as progress to resist against a culture that is very much male-dominated," he said at the event, where he met with his employees at the South Chungcheong Provincial Government building.
"I hope the movement can be an opportunity for us to make a fairer and more peaceful society."