A key opposition lawmaker at the center of a political firestorm on Wednesday dropped her plan to leave the party as she vowed to make efforts to strike a deal on a controversial bill regarding the investigation of April's ferry disaster.

Park Young-sun, floor leader of the main opposition New Politics Alliance for Democracy, had suggested that she could quit her leadership post and even leave the party due to infighting over the formation of its interim leadership.

"I am sorry for causing much concern at a critical moment," Park said in a news conference.

She also pledged to assume responsibility and make the utmost efforts to reach an agreement on the bill designed to uncover the truth behind the ferry disaster.

Park's move is widely expected to help resume negotiations between the rival parties on how to work out differences on the bill.

Park and her ruling party counterpart produced a second deal on the bill last month, but the opposition party did not endorse it.

Complicating the matter, the families of the ferry victims rejected two successive deals by the ruling and opposition parties on the bill.

The opposition and the victims' families have demanded that a fact-finding committee be granted the authority to investigate and indict those responsible for the ferry sinking that left more than 300 people dead.

On Tuesday, President Park Geun-hye ruled out concessions as she called on the parliament to quickly pass the bill, warning that the demand from the opposition and victims' families could undermine the country's judicial system. (Yonhap)