The main opposition party slammed the ruling party's plan for a speedy approval of the prime minister nominee Tuesday, vowing "exhaustive" parliamentary scrutiny of the candidate.

The move by New Politics Alliance for Democracy  floor leader Lee Jong-kul came as his ruling Saenuri Party counterpart, Yoo Seong-min, announced a parliamentary plan last week to endorse prime minister nominee Hwang Kyo-ahn before President Park Geun-hye's scheduled trip to the United States in mid-June.

Park appointed Hwang, the current justice minister, to the country's second-highest official position last week, with the opposition bloc severely resisting the choice of a former prosecutor who championed the controversial National Security Law.

"It is a matter that is subject to (bipartisan) negotiations and it cannot be done unilaterally," Rep. Lee said during a party meeting, expressing "regrets" over the Saenuri Party plan.

NPAD has yet to agree to the approval plan, the opposition floor leader said.

"Whether the PM candidate is eligible will be thoroughly examined in line with citizens' perspective." he said.

The presidential office Cheong Wa Dae plans to submit a motion seeking parliamentary approval to the National Assembly later in the day. (Yonhap)