Updated

South Korea's president has decided to retain the country's current prime minister -- who holds the No. 2 spot in the government -- after two possible replacements for the job both abandoned their nominations because of questions over past behavior, officials said Thursday.

Prime Minister Chung Hong-won had offered to step down after April's ferry disaster as a way to assuage enormous public anger over the tragedy, which left more than 300 people dead or missing. President Park Geun-hye tried to replace him and reshuffle other Cabinet officials to try to win back public trust.

But her two subsequent choices for prime minister withdrew their names even before their confirmation hearings began -- one on Tuesday amid criticism over his past comments that allegedly supported Japan's 1910-45 colonial rule of Korea and the other last month over alleged ethical lapses.

The two consecutive withdrawals dealt a blow to Park, whose approval rating has plummeted after the disaster.

On Thursday, senior presidential official Yoon Doo-hyun said in a televised briefing that Park has now rejected Chung's resignation offer and asked him to stay on to prevent a further vacuum in state management. Chung said he agreed, and that he would strive to help Park press ahead with reform measures promised after the sinking.

South Korea's executive power is concentrated in the president but the prime minister leads the country if the president becomes incapacitated. A person nominated for the job must be approved by the National Assembly.

It's not clear whether Chung's retaining would help Park facing mounting political offensive by her rivals. The main liberal opposition party on Thursday criticized Park's decision, calling it an acknowledgement of her government's incompetence.

Some of Park's choices for other Cabinet ministers have already faced snowballing criticism over their past behaviors such as alleged plagiarism of research papers. They are required to undergo parliamentary hearings, although their appointments don't need legislative endorsements.