The Eastern Cape ANC has rejected the outcome of a unanimous vote by the OR Tambo region for Deputy President Kgalema Motlanthe to lead the party.
Provincial secretary Oscar Mabuyane told the South African Press Association the meeting in Mthatha was "irregular" and "not properly convened".
"The meeting was flawed. It was not properly convened and was not a formal meeting. It is neither here nor there that we accept the outcome or not."
The Eastern Cape ANC was due to nominate leaders for the party's national elective conference in Mangaung in December, at the University of Fort Hare, in Alice, on Thursday. The Eastern Cape is the ANC's second-largest region of support.
The conference, scheduled to start at 2pm, was postponed to Friday to allow the party time to verify the credentials of delegates.
Earlier this month, the ANC in the Eastern Cape was hit by reports of "ghost members" on its membership book. Databases from public and private institutions had been used to obtain people's details and enrol them, Mabuyane said. Some were not even aware they were ANC members.
The culprits had also deposited R12 joining fees, so the ghost members were in "good standing".
Mabuyane said the problem was discovered when the membership register was checked ahead of branch meetings to discuss the Mangaung conference.
"The national audit team has finalised its work of verifying the delegates. Once that has been done we can proceed," he said.
On Wednesday the OR Tambo region unanimously voted to nominate Motlanthe to lead the party.
The Daily Dispatch reported that all 107 delegates at the meeting supported Motlanthe to take over as ANC president, with Human Settlements Minister Tokyo Sexwale as his deputy and Sports Minister Fikile Mbalula as secretary general.
Regional chairperson Thandekile Sabisa told the South African Broadcasting Corporation on Wednesday that under Zuma the party had failed to address issues raised at the 2007 Polokwane conference.
"The use of state power, factionalism, ill-discipline, etc ... This leadership has failed to address those issues. It's not credible, it's under attack and not respected by opposition parties," he said.
"We then said, let's find leadership that will be respected by the people of South Africa and the membership of the ANC. Comrade Kgalema Motlanthe, we believe, is the one that would bring back the dignity of the organisation."
The Eastern Cape would take 676 delegates, the second-biggest delegation, to the ANC's leadership election in December. – Sapa