SEOUL (Reuters) - South Korean opposition parties differed on Thursday on when to bring an impeachment motion against scandal-tainted President Park Geun-hye and were far apart from her conservative party on her offer to quit.

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Park on Tuesday asked parliament to decide how and when she should step down in a dramatic turn of events in the influence-peddling scandal, an offer that the main opposition Democratic Party rejected as a ploy to buy time and avoid impeachment.

The smaller opposition People’s Party on Thursday warned against bringing an impeachment motion to the floor of parliament without ensuring the support of Park’s Saenuri Party, which would be needed for it to pass.

“If the motion is voted down, it is effectively a remission of her sins,” People’s Party chief Park Jie-won told a party meeting.

But the leader of the Democratic Party, Choo Mi-ae, insisted on an immediate motion so she can be out of office by the end of January.

Park Jie-won, who is not related to the president, has said he would also consider bringing the motion to a vote next Friday and indicated his party was open to negotiating how the president should leave office and when.

President Park has been under pressure to step down over allegations by prosecutors that she colluded with a friend to allow her improper influence in state affairs and in fundraising for two foundations set up to back her policy initiatives.

She has denied wrongdoing but acknowledged she would need to step down to end the turmoil, amid a series of large protests bringing hundreds of thousands of people to the streets of Seoul on Saturdays.

The three opposition parties together hold 165 of the single-chamber parliament’s 300 seats and can initiate an impeachment motion.

But they need support from at least 28 Saenuri members for it to pass.

The vote, if successful, has to be reviewed by the Constitutional Court, which can take up to 180 days. Legal experts have said the review could be over in a third of that time.

Kim Moo-sung, a Saenuri leader who has called for Park’s resignation, said after meeting Democratic Party leader Choo that he had proposed that Park leave office by the end of April so an election can be held around the end of June.