More senior South African public figures came out on Friday to accuse a business family with close ties to President Jacob Zuma of exerting undue influence, as top ANC officials met to discuss the most serious political crisis in nearly a decade.

The scandal comes at a time when the ruling African National Congress is at a crucial stage with local elections after May, in which it will face stiff competition from the opposition in the economic hub of Johannesburg and capital Pretoria.

However, as he answered questions in parliament on Thursday, Zuma did not have the air of a man fearing for his political future. The NEC is stacked with Zuma loyalists, and is unlikely to turn against the party leader, analysts say.

Zola Tsotsi, who resigned a year ago as chairman of state power firm Eskom, told the Mail & Guardian newspaper his exit was orchestrated by the Guptas, who were accused this week of offering cabinet posts to two ANC politicians.

"Two months after the appointment they called me and said they will have me fired because I am not playing the game. I was forced to resign shortly after that," Tsotsi told the weekly.

A spokesman for the Guptas was not immediately available for comment. The family this week denied ever trying to influence political appointments, saying they were the victims of a politically motivated plot.

The latest scandal involving the Guptas, a family of Indian-born businessman who moved to South Africa at the end of apartheid in the early 1990s, has added to waning investor confidence that has sent the rand on a roller-coaster.

The ruling African National Congress' top decision-making body - its National Executive Committee - holds a scheduled meeting from Friday to Sunday at which the scandal is set to hold top billing.

The ANC's secretary general Gwede Mantashe said on Thursday that the party had not discussed whether to remove Zuma.

Job offer

Pressure mounted on Zuma this week after deputy finance minister Mcebisi Jonas said he had been offered the job of finance minister last year, shortly before Zuma fired the respected Nhlanhla Nene from the position.

Former ANC Treasurer Matthews Phosa said the mountain of evidence pointing towards an unhealthy relationship between the Guptas and Zuma, whose son sits on the boards of at least six Gupta companies, was growing.

"This sensation is repeating itself ad nauseam. We are beginning to wonder whether those who say it is not true are themselves being genuine," Phosa told Talk Radio 702. "I think it is true and I think the Guptas must stop it."

South Africa's leading financial newspaper, Business Day, said the ANC had to act to curb the Guptas influence but doubted it would go as far as ditching Zuma - as it did with Thabo Mbeki in 2008.

Mbeki was ousted in what was then the most dramatic political crisis since the end of apartheid. The party recalled Mbeki before his term ended, and he agreed to step down.

"Forgive the cynicism but the few voices against the ANC's colonisation by Zuma and his family benefactors does not yet constitute a groundswell," it said in an editorial.