The leaders of the ruling Democratic Party (DP) resigned en masse Thursday to take responsibility for the shocking rout in this week's by-elections.

"Taking responsibility for the results of the elections, all (members of) the DP leadership are stepping down," Rep. Kim Tae-nyeon, the party's acting chairman and floor leader, said in a press conference at the National Assembly.

The party will hold a convention to pick a new chairman on May 2, a week earlier than initially planned, and an election for a new floor leader on Friday next week, according to party officials.

"Through the election this time, the people have given the DP a lot of tasks," Kim said and promised thorough efforts for innovation.

In a following meeting, the party's supreme council also designated three-term party member Rep. Do Dong-hwan as the chairman of the emergency response committee, which will steer the party until the new leadership takes office. The council also assigned the committee to the task of replacing the seven-member supreme council.

The party with 174 members in the 300-seat National Assembly suffered a crushing defeat in Wednesday's by-elections for 21 local posts, including the mayors of Seoul and Busan. (Yonhap)