South Korea's conservative ruling party is on the verge of a split following President Park Geunhye's parliamentary impeachment last week.

Kim Moo-sung, leader of anti-Park lawmakers in the Saenuri Party, on Tuesday called Park loyalists her "political slaves" in an escalation of harsh rhetoric between rival factions in the largest political party in South Korea.

He told a televised conference that he and fellow lawmakers are considering leaving the party to create a new political group.

The feuding has intensified after dozens of Saenuri Party lawmakers aligned with a coalition of liberal opposition lawmakers to impeach Park on Friday because of a scandal involving her longtime, shadowy confidante.

Park supporters in the party criticized anti-Park members for betraying the embattled leader and told them to leave the party.

"It's really hard to tolerate the fact that some people, who had enjoyed all the benefits and political conveniences under the big 'Park Geun-hye' roof, took the initiative in the impeachment in a harsher manner than opposition parties," Choi Kyung-kwan, a senior party member who served as Park's finance minister, said on his Facebook page on Monday.

But Kim said it was Park who betrayed the public and the party, describing her ties with her loyalists as similar to those of "gangsters".

Park's presidency will formally end if the Constitutional Court approves the impeachment. That would lead to an election to pick her successor.

If that happens, then the anti-Park lawmakers could try to establish a new political party involving outgoing UN Secretary-General Ban Ki-moon and some liberal opposition politicians. Ban has not said if he would run for president, but opinion polls put him in second place behind Moon Jae-in, a former leader of the main opposition Democratic Party, to replace Park.

The scandal resolves around allegations that Park allowed her friend of 40 years, Choi Soon-sil, to manipulate government affairs and extort money from businesses. Choi and several top presidential and government officials have been indicted over their alleged roles with the scandal. Park has avoided prosecutors' questioning because she has immunity from prosecution while in office.