South Korea's opposition People's Party will start collecting signatures for an impeachment motion against President Park Geun-hye, while the main opposition Democratic Party reviews conditions for impeachment.
It comes after South Korean prosecutors said on Sunday they believed Park was an accomplice in an influence-peddling scandal that has rocked her administration.
Park's close friend Choi Soon-sil and former presidential aide An Chong-bum have been charged with abuse of power by pressuring companies to contribute funds to foundations at the centre of the scandal.
Hundreds of thousands of people took to the streets of Seoul on Saturday in the fourth straight weekend of protests against Park, in the biggest public demonstrations the country has seen since the 1980s.
Park, who's five-year term ends in February 2018, has resisted calls to resign but has apologised twice, saying she only sought to benefit the economy not herself, but acknowledges carelessness in her ties with Choi.
