Former South African Defence Minister Mosiuoa Lekota says it is inevitable that the ruling African National Congress will split.
He told the BBC on Wednesday that "divorce papers" were being served.
Mr Lekota announced a conference will be held in the next few weeks where a decision may be taken to split from the ANC.
Mr Lekota is a close ally of former President Thabo Mbeki who was forced to step down last month and was one of several ministers who resigned along with Mr Mbeki.
General elections are due in South Africa in the first half of next year.
The BBC reports the ANC is divided between supporters of Mr Mbeki and Jacob Zuma, who won a bitter contest to become ANC party leader last year.
Mr Lekota is a former ANC chairman. He did not refer to Mr Zuma by name but condemned tribalism and ANC leaders who "stand on public platforms singing songs that advocate violence".
Some of Mr Zuma's supporters celebrate his Zulu origins, while his trademark song is the apartheid-era anthem "Bring Me My Machine Gun".
In an open letter last week, Mr Lekota accused the new ANC leadership of damaging democracy.
Supporters of Mr Zuma have been accused of intimidating the judiciary during his recent legal problems.
Mr Zuma's supporters accused Mr Mbeki of being too aloof and business-friendly but Mr Zuma has said he would not change South Africa's economic policies, if he does become president next year.