Prime Minister Lee Wan-koo fell deeper into his quagmire on Thursday as his choice of words and inconsistent explanations of graft allegations against him led the opposition to escalate calls for his resignation.

Lee altered his stance on joining President Park Geun-hye’s campaign trail in 2012 and how well he knew the deceased former Keangnam Enterprises chief Sung Woan-jong.

Lee has found himself the main target of the opposition’s ire in the graft scandal sparked by a testimony and a memo left by Sung before he killed himself last week, alleging that he illicitly delivered money to eight political heavyweights.

During Thursday’s interpellation, Lee said he did not remember meeting Sung during his run for a parliamentary seat in 2013. The comment ran counter to his earlier remarks to local media that he never met him alone.

When Rep. Yoo Dae-un of the main opposition New Politics Alliance for Democracy accused him of flip-flopping, he replied, “What I meant was that I have no recollection of such a meeting.” Lee said he could have been misunderstood because of his Chungcheong Province dialect.

Lee’s comments came after several of Sung’s former employees and aides testified that the two had a private meeting. Prior to his death, Sung claimed that he handed Lee 30 million won ($28,000) during the supposed meeting at his campaign office two years ago.

Lee had denied having a personal relationship with Sung, but after a memo surfaced showing that the two had met 23 times over the past 20 months, he said that Sung could have been one of the Saenuri Party members that he met several times a day as he was floor leader of the party.

In what has been viewed as an attempt to undermine his relationship with Sung ― who was formerly a member of a President Park Geun-hye’s 2012 election committee ― Lee claimed that he did not participate in the campaign as he had blood cancer. But after a video of him urging support for Park at a rally emerged, he admitted that he participated in “two or three” rallies.

Lee’s unconventional choice of words has also hurt him. He pledged Tuesday to “end his life” if any evidence of him receiving money from Sung turned up. These words sparked a cold reaction from opposition lawmakers and even some ruling party members.

“I think was I too emotional when I said it, and I’ve already apologized yesterday (for the comment),” he said Thursday.

Despite mounting pressure to step down, Lee maintained that he would continue to carry out his duties as the premier.

The NPAD stepped up their offensive and said they could choose to push for Lee’s impeachment.

“If (the prime minister) himself does not step down and the president continues to do nothing about the situation, our party has no choice but to take a more drastic decision,” NPAD leader Rep. Moon Jae-in told reporters.

Under Korean law, one-third of National Assembly members have to consent to propose a premier’s dismissal, and a majority has to agree in order for it to be passed.

As the graft scandal shook the political circles, the prosecution stepped up its probe into Keangnam Enterprises by raiding the company’s headquarters along with residence of 11 of Sung’s aides. They also summoned a 43-year-old confident of Sung surnamed Lee, who worked as his secretary and aide during Sung’s tenure at the National Assembly.

The investigation focused on tracking the money flow that leaked from the company, which may have been used for illegal lobbying.

Meanwhile, additional release of Sung’s interview with the Kyunghyang Shinmun newspaper showed that Sung believed he became the target of the prosecutorial investigation for his close relationship with U.N. Secretary-General Ban Ki-moon, who is often considered a prospective candidate for next presidency.

Sung had reportedly contacted several politicians to raise support for Ban while Ban’s brother had worked for Keangnam Enterprises.

By Yoon Min-sik (minsikyoon@heraldcorp.com)