"If Hwang does not give the approval, he would be violating the law. As he would be violating his authority, that act constitutes as grounds for impeachment by parliament," Rep. Woo Sang-ho, the floor leader of the Democratic Party, said during an interview with CBS Radio.

While opposition parties have been urging that the acting president to approve the extension, the ruling Liberty Korea Party has been protesting against it, apparently because prolonging the probe could have an adverse impact on the party's chances in the next presidential election, which may come as early as May.

Woo said Hwang is obligated to extend the investigation if the probe lacks progress, and that he does not hold the right to decide on yes or no.

The floor leader, however, said the party is trying its best to avoid the impeachment of Hwang, although warning an abuse of authority would result in a "grave situation."

Park was impeached by the parliament in December on allegations that her confidante Choi Soon-sil exerted influence on state affairs without any position in the administration, while seeking to extort money from conglomerates. (Yonhap)