A breakaway faction of South Africa's governing African National Congress has been meeting in Johannesburg to look at establishing a new political party.
Addressing more than 6,000 delegates, the faction's leader, Mosiuoa Lekota, accused the ANC of abusing its power.
The former defence minister said a new party was needed to prevent the country from returning to apartheid-style rule.
The opposition leader, Helen Zille, said the convention could be a "turning point" for democracy in South Africa.
"The ANC should be very afraid," warned the head of the Democratic Alliance, one of several political parties which attended the gathering.
The launch of the new party - as yet unnamed - will take place on 16 December in Free State province, Mbhazima Shilowa, a former provincial premier, announced at the meeting.
Mr Lekota, who resigned as defence minister and spearheaded the breakaway after last month's forced resignation of President Thabo Mbeki, opened the convention to applause with a traditional ANC chant of "Amandla", or "Power", according to the AFP news agency.
He said the ANC dissidents had chosen to represent the views of the South African people.
"We have no apology to anybody. We have decided and we are ready to fight as messengers and representatives of hope for the people," he told delegates.
Mr Lekota said the "dominant political forces" in the country - the leaders of the ANC - were "determined to abuse their power to advance their personal interests" as white minority government had done during apartheid.
"The threat the nation faces is that we will see the reaffirmation of important elements of that terrible legacy under our new masters," he added.
"Shall we keep quiet and do nothing as we see the open betrayal of everything people saw as their hope for their future?" he asked to cries of "No!"
Mr Zuma says the party is unfazed by the upheaval of recent weeks but with a general election just months away, analysts believe the ANC's troubles may affect its campaign.
The infighting stems from a power struggle between Mr Mbeki and Jacob Zuma, who defeated Mr Mbeki to become party leader last December.
Mr Mbeki stood down in September after a judge suggested he may have interfered in the prosecution of Mr Zuma on corruption charges. Mr Mbeki strongly denies the claim.
His ousting led ex-defence minister Mosiuoa Lekota and other loyalists to quit the ANC in protest.
Mr Lekota, a former ANC chairman and leader of the breakaway movement, officially resigned from the party on Friday.
The disaffected ANC members accuse the party of undermining South Africa's young democracy.
The political schism marks a dramatic shake-up in a country where the ANC has dominated political life since the end of white-minority rule in 1994.
The ANC won more than two-thirds of votes in the last election and controls a strong majority in parliament.