South Korea's main opposition party, engulfed in an internal feud over its policy toward President Park Geun-hye's handling of the aftermath of April's deadly ferry disaster, selected a five-term lawmaker as its new interim leader.

Moon Hee-sang, 68, is set to be formally appointed as the interim leader of the New Politics Alliance for Democracy on Friday, party officials said.

"I feel a sense of heavy burden to assume the party's interim leader," at a time when the party is in a difficult situation, Moon said after he was named the new leader at a meeting of the party's senior lawmakers.

Moon also appealed to the people and party members to support the opposition party.

Moon is tasked with, among other things, putting the party rocked by infighting over the formation of its interim leadership back on track, party officials said.

His term is set to expire early next year, when the opposition holds a national convention to select a new leader.

Moon's selection came a day after the opposition's floor leader, Park Young-sun, dropped her plan to leave the party amid infighting. Park had threatened to bolt the party after hardliners attacked her for being too soft to the government, especially over the ferry disaster that claimed the lives of nearly 300 people, most of them high school students.

The opposition leader, who wears two hats -- the party's floor leader and interim supreme leader -- returned to work on Wednesday, but she quit her job as the party's interim leader in just over a month after she won the party's top post following a crushing defeat in parliamentary by-elections in July.

NPAD won only four of the 15 parliamentary seats up for grabs in the by-elections, prompting party co-leaders Kim Han-gil and Ahn Cheol-soo to step down to take responsibility for the defeat.

The new interim leader-to-be served as chief of staff to then President Roh Moo-hyun in 2003-2004 and deputy speaker of the National Assembly in 2008-2010. He also had served as interim leader of the opposition's predecessor following the party's defeat in the presidential election in December 2012. (Yonhap)