SEOUL - All members of South Korea's biggest opposition party will resign their parliamentary seats unless the bill to impeach President Park Geun-hye is passed through the National Assembly, the party's whip said Thursday.

Minjoo Party's Floor Leader Woo Sang-ho said senior party members agreed that all party lawmakers would vacate their seats if the impeachment motion is not passed through the unicameral assembly. The bill is scheduled to be put to vote on Friday.

The biggest opposition party is set to hold its general meeting later in the day before submitting the resignation en bloc to the party leadership, according to Yonhap news agency report.

The minor opposition People's Party is reportedly collecting signatures on the resignation en bloc unless the impeachment bill is passed in the 300-seat parliament.

The impeachment bill was put forward last Saturday by opposition and independent lawmakers, but at least 28 ruling Saenuri Party lawmakers must vote for it to overcome the two-thirds threshold. The governing party has 128 parliamentary seats.