The National Assembly held a plenary session, but the revision of the bill, which enabled the independent counsel team to investigate the corruption scandal, was not put to a vote as the Liberty Korea Party objected to it.

The bill allowed the special prosecutors to end their probe by the end of this month. Prime Minister Hwang Kyo-ahn, who is serving as a caretaker president following Park's impeachment in early December, can extend it for up to 30 days, but Hwang has refrained from accepting the extension.

Four opposition parties sought in vain to put the revised bill, which will lengthen the probe for 50 days, to a vote.

The parliamentary speaker of the main opposition Minjoo Party has a right to table a bill, but the right is limited to emergency situations such as natural disasters and national emergency. The speaker hesitated to exert his right on Thursday.

The independent counsel team has asked for the extended investigation as it has yet to look into additional cases involving the heads of major conglomerates, called chaebol here.

Samsung Electronics Vice Chairman Lee Jae-yong has been taken into custody for bribery charges, but probe into other conglomerates has yet to kick off because of lack of time allowed.

Unless the special investigation is extended, state prosecutors would continue to probe other suspicions. It would cause concerns about political neutrality as the state prosecutors are still being influenced by the acting president.