The woman named by South African media as the future wife of ex-president Jacob Zuma has been forced to resign from her position at a women's rights charity, the group said Monday.
The She Conquers foundation, which campaigns to improve the lives of adolescent girls, said Nonkanyiso Cono "failed to disclose her relations with Mr Zuma" and had acted "contrary to the principles" that the charity stood for.
"As young girls we are lured and used by people with power who use their position to take advantage of us," the group said in a statement.
According to media reports in South Africa, Cono, 24, is due to become the new spouse of 76-year-old Zuma who currently has four other wives.
The Sunday Times weekly reported that Cono had been a frequent visitor at Zuma's residence east of Johannesburg since she was 19.
The former president, who was forced to resign in February after nearly a decade in power, is facing a string of corruption charges stemming from an arms contract dating to before his time in office.
His political career was dogged by controversy and he was in 2006 acquitted on charges of raping a HIV-positive woman.
He also caused outrage among health campaigners by telling the court that he had showered after having unprotected sex with his accuser to avoid contracting the virus.