The main opposition party will not renegotiate a bill aimed at uncovering the truth behind April's deadly ferry sinking despite the wishes of family members of the victims, the party's interim chief said Wednesday.

On Tuesday, the ruling Saenuri Party and the No. 1 opposition party New Politics Alliance for Democracy (NPAD) reached a deal to pass the bill after weeks of wrangling over who should have the right to choose a special counsel for the investigation.

The investigation is aimed at determining the truth behind one of the country's deadliest maritime accidents as critics argue that the government's initial failure to properly respond to the disaster contributed to the high death toll.

The 6,825-ton ferry Sewol capsized off South Korea's southwest coast on April 16, leaving more than 300 people dead or missing.

Most of them were high school students on a field trip to the southern resort island of Jeju.

In Tuesday's deal, the rival parties agreed that the ruling party would appoint its share of a seven-member panel to be tasked with choosing the special counsel only after seeking the approval of the opposition party and family members of the victims.

The deal was met with immediate objections from the families, who argued that the ruling party should not be allowed to select any of the members.

By law, the ruling and main opposition parties each select two members for the panel, which then recommends two special counsel candidates to the president. The president appoints one of the two.

The deal was approved with applause at a meeting of ruling party lawmakers on Tuesday, but NPAD lawmakers deferred their decision amid opposition from the victims' families.

The development is a new twist on efforts by President Park Geun-hye's government to put the tragedy behind it and move on to address a host of pressing national issues, including rebuilding the sluggish economy.

The opposition party also faces another challenge as it has already broken a previous deal with the ruling party to follow the law in choosing members for the special counsel.

Park Young-sun, NPAD's interim chief and floor leader, acknowledged that Tuesday's deal failed to satisfy the demands of the bereaved families.

"We must understand their stance," she told Yonhap News Agency after meeting with the father of a victim, who has been staging a hunger strike in central Seoul for nearly 40 days.

On the families' demands for another renegotiation of the bill, however, she said, "I told them that can't be done." 

Instead, the opposition leader asked President Park to meet one of the victim's father who has been staging a hunger strike over a month to help resolve the prolonged standoff.

The presidential office, however, distanced itself from the bill. 

"The special law on the Sewol incident is a matter that needs a bipartisan agreement, not something President Park can decide," presidential spokesman Min Kyung-wook told Yonhap News by phone. (Yonhap)