The African National Congress (ANC) is riddled with nepotism, tribalism and corruption, charged former South African President Thabo Mbeki in a scathing attack on the ruling party and former liberation movement that he has served all his life.

Mr Mbeki, who became the second black president of South Africa in 1999 after Nelson Mandela retired and who was ousted in September, gave warning that he would not campaign for the ANC at the elections next year.

In a stinging attack he went on to accuse Jacob Zuma, his rival and the current ANC leader, of creating a “noxious” cult of personality more in keeping with Kim Il Sung, the late North Korean leader, than the democratic traditions of the oldest African liberation movement.

Mr Mbeki, 66, stopped short of endorsing the plans of a breakaway faction to set up a new party, but his letter made clear where his sympathies now lie. The former president angrily declared that announcements by the ANC that he would campaign on their behalf “took me by surprise”.

“I appeal that nobody should abuse or cite my name falsely to promote their partisan cause, including how the 2009 ANC election campaign would be conducted,” he wrote.

On the eve of a national convention to prepare for the new party, Mr Mbeki rebutted earlier leaks of selected parts of his letter by the ANC leadership suggesting that he was distancing himself from the actions of the rebels' leader Mosiuoa Lekota, the former Defence Minister.

Mr Lekota, nicknamed “Terror” for his prowess on the football field, has called all those opposed to the ANC to a weekend conference to discuss the form the new party should take and examine issues such as a possible electoral pact with other opposition parties.

Yesterday Mr Lekota, who along with several other dissidents had been suspended from the ANC, resigned formally. He said he regretted that the current leadership had deviated from the historic principles of the ANC for which he served many years in prison on Robben Island.

Other Mbeki loyalists have rallied to Mr Lekota, a free-marketer detested by allies of Mr Zuma on the left of the party.

In his letter, however, Mr Mbeki said that the loyalists - most of whom resigned when he was unceremoniously kicked out of office - had not sought his approval but admitted that he had informally counselled all sides to “address all matters that might be in contention”.

“I have noted that some in our broad democratic movement have spoken publicly, unfortunately and wrongly, saying that Comrade Terror and others have acted as they have, driven by their loyalty to me as an individual,” he wrote. “I find it strange in the extreme that today cadres of our movement attach the label of a ‘cult of personality' to me and indeed publicly declare a determination to ‘kill' to defend your own cause, the personal interests of the ‘personality', Jacob Zuma.”

Mr Mbeki penned the tirade in a private letter this week and was reportedly furious when the ANC leaked selected sections, giving the impression that he would campaign for the mainstream movement and against the dissidents.

“I could not understand how the same ANC which was so disenchanted with me could within a fortnight consider me such a dependable cadre as could be relied upon to promote the political fortunes of the very same movement which I had betrayed in such a grave and grevious manner as to require that I should be removed from the presidency,” he declared.

Mr Zuma is accused of corruption and bribery in a multibillion-pound arms scandal, but is set to be the ANC candidate for president. His supporters on the left of the party maintain that he is the victim of an Mbeki-inspired conspiracy.

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