South Korea's prime minister post: The roles and past resignations

South Korean Prime Minister Lee Wan Koo, who took office in February, offered to resign on Tuesday (April 21) over a bribery scandal that has brought President Park Geun Hye's approval rating to a near-record low.

The scandal has made headlines since businessman Sung Wan Jong was found dead in early April with a note showing the names of officials and indications of sums of money. Before his death, the head of Keangnam Enterprises had allegedly told a local newspaper that he had given 30 million won (S$37,500) to Mr Lee in 2013 and 200 million won (S$250,000) to a member of Ms Park's presidential campaign team in 2012.

If his resignation is accepted by the president, Mr Lee will make history as one of the shortest-serving prime ministers in South Korean history. Here's what you should know about the country's premiership:

What's the role of prime minister?

The prime minister is appointed by the president with the National Assembly's approval. He has limited responsibilities that include leading the Cabinet, supervising ministries and making recommendations for ministers.

The position is largely a ceremonial one in South Korea, where power is concentrated on the president.

It is common for a prime minister to resign to take the blame for some policy failure, scandals or major crises. He could also resign because of a serious mid-term defeat or as a consequence of a decline in approval ratings for the president.

Why past PM nominees withdrew candidacy?

Mr Lee was President Park's third nominee to replace Prime Minister Chung Hong Won who offered to step down last year over the government's handling of the Sewol ferry sinking. Her previous two nominees withdrew their candidacy even before confirmation hearings: Mr Ahn Dai Hee, a former supreme court justice, was forced to withdraw his nomination following a controversy over income he amassed after leaving the bench and going into private practice. The second nominee, Mr Moon Chang Keuk, withdrew his nomination because of a speech he made in 2011, calling Japan's 35-year occupation of the Korean Peninsula "God's will".

Which other PMs resigned?

Mr Chung Hong Won (2013-2015):

He resigned on April 27 last year amid rising anger over the government's handling of the Sewol ferry sinking on April 16 that left more than 300 people dead or missing. President Park accepted the resignation in principle but retained him to lead the Cabinet after Mr Ahn and Mr Moon withdrew their nominations. Mr Chung was formally replaced by Mr Lee on Feb 16 this year.

Mr Chung Un Chan (2009-2010):

He offered to resign on two occasions in 2010 - for the party's defeat in regional elections and for failing to win parliamentary approval to stop relocation of government offices to the newly created Sejong City in central South Korea. Mr Chung had insisted it would be inefficient and "almost paralysing for government operations" to move to Sejong city. It was for this reason that he eventually stepped down on Aug 10, 2010.

Mr Han Seung Soo (2008-2009):

Mr Han and his entire cabinet offered their resignation to then President Lee Myung Bak over a US beef dispute on June 10, 2008. They took responsibility for the intensifying political turmoil triggered by the government decision in mid-April to unconditionally lift a ban on US beef imports. This was despite demands by hardline civic activists and opposition parties to renegotiate the deal to completely ban imports of all dangerous cattle by-products.

Ms Han Myeong Sook (2006-2007)

Ms Han was South Korea's first and so far only female prime minister. She resigned from her position on March 7, 2007, amidst speculation that she would run in the December 2007 presidential elections. She later declared her presidential candidacy but did not win the election.

Mr Lee Hae Chan (2004-2006):

Mr Lee resigned on Mar 14, 2006 for playing golf when he was supposed to be overseeing the government's response to a national railway strike. He was not working on Mar 1, the first day of a nationwide walkout by railway workers which coincided with a national holiday marking Korea's 1919 civil uprising against Japanese colonial rule. He was heavily criticised because in South Korea, people expect high-level officials to work overtime during times of crisis.

Mr Goh Kun (2003-2004):

He resigned on May 24, 2004 after refusing to comply with then-President Roh Moo Hyun's request to name nominees to three cabinet posts, saying it violated the intention of the constitution.

SOURCES: THE STRAITS TIMES ARCHIVES, REUTERS, AFP, NEW YORK TIMES, BBC, CNN