Jacob Zuma, South Africa’s most controversial politician, defeated Thabo Mbeki to win the presidency of the ruling African National Congress (ANC) — in the process dealing his arch rival an unprecedented humiliation and putting himself firmly in line to be the country’s next president.

After two years of bitter political in-fighting, the most divisive ANC conference on record resulted in Mr Zuma defeating Mr Mbeki, the South African President, by 2,329 votes to 1,505.

The rebuke to Mr Mbeki, which may prematurely end his political career, was enhanced by pro-Zuma candidates taking a clean sweep of the top six positions on the party’s National Executive Committee.

Chaos erupted in the hall as the result was delivered, with delegates pumping their fists in the air while, outside, fireworks lit up the night sky. “It’s a whitewash, a clean sweep,” shouted one Zuma supporter while another delegate screamed into his mobile phone: “The members have taken back the party.”

A stone-faced Mr Mbeki, who dismissed Mr Zuma as the country’s Vice-President in 2005 after he was named in an arms corruption scandal, embraced his rival on the stage after the results were read out.

Obliged to step down as President of South Africa in 2009, Mr Mbeki had hoped for a third term as party leader so he could name his succesor and secure his legacy as the architect of the longest period of growth for Africa’s largest economy since the Second World War. But Mr Zuma’s resounding success will increase the pressure on Mr Mbeki to hold presidential elections before 2009. Victory capped a remarkable comeback for the populist Mr Zuma, who is now almost certain to become the ANC’s candidate for president in 2009.

It is an election he is assured of winning, given the ANC’s continuing political dominance in the country 13 years after the end of apartheid. The only threat to his candidacy appears to be fresh corruption charges being brought against him after defeat in a recent court bid to have a series of search warrants declared illegal. Securing the presidency would give him judicial immunity.

Commentators speculated that the victory was a watershed moment for the country, now in its second post-apartheid decade as a democracy. But the prospect of a Zuma presidency terrifies many South Africans, who fear the country is in real danger of repeating the mistakes of many post-independence African nations.

Foreign investors have also indicated much concern over recent developments, despite a recent charm offensive from Mr Zuma, who says that the country’s market-friendly policies will remain. Critics blame Mr Mbeki’s downfall on his arrogance and detachment from the party’s grassroots. His refusal to accept dissent and his blind support of loyal, but incompetent, ministers, particularly in the areas of health and crime, has fed a grassroots’ rebellion.

Mr Zuma, who portrayed himself as the victim of a political conspiracy, found a willing constituency on which to build an amazing political comeback. As well as fighting corruption charges, he was acquitted last year in a rape case involving a family friend who was half his age — although he was widely ridiculed for testifying that he had showered after sex with his HIV-positive accuser in order to prevent infection. A former detainee on Robben Island and leader of the ANC’s military wing, Mr Zuma has long been one of the most popular leaders among the party’s militants. He portrayed himself as the champion of the poor, particularly the 40 per cent of the black population that is no better off today than at the end of white rule in 1994.

His earthy charm contrasts sharply with the aloof Mr Mbeki, an intellectual with a penchant for quoting Shakespeare and a distaste for street politics and the mob.

The conference, which opened on Sunday, has been marred by ugly scenes unthinkable during the long struggle against apartheid, when the ANC prided itself on its discipline and unity, at least in public. Delegates supporting different factions at the first contested leadership election in more than 55 years taunted and jeered one another and senior party figures struggled to maintain order.

Although Mr Mbeki can point to an uninterrupted period of growth, unemployment is unofficially estimated to be about 40 per cent. He served as deputy president to Nelson Mandela before taking power in 1999.

Kgalema Motlanthe, a former trade unionist, easily took the post of Deputy President — a position that could take on particular significance if Mr Zuma were forced to step down if convicted on the corruption charges.

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president