The ANC in the Free State will re-run its elective conference in March next year, secretary-general Gwede Mantashe said on Saturday night.
"As a result the province will be leaderless... So a provincial task team will organise the conference within three months of the new year," Mantashe told reporters in Bloemfontein.
The national executive committee (NEC) took the decision at a meeting on Saturday to uphold a Constitutional Court judgment which declared the provincial conference invalid.
Mantashe said the Free State provincial executive committee (PEC) would be replaced by a task team.
The 20 member PEC would not be allowed to attend the African National Congress' conference starting on Sunday in Mangaung.
However, Free State delegates, who were not part of the leadership, would still attend and vote.
Provincial chairman Ace Magashule, was the only PEC member who would still attend the conference as an elected NEC member.
ANC head of policy Jeff Radebe said the Constitutional Court was the final decision-maker on constitutional matters.
"It is the final [decision] on this matter."