South Africa's chief prosecutor, who has led a spirited anti-corruption campaign against top South African politicians, has resigned, sparking allegations that he has been forced to quit by a political establishment fearful of his work.

South Africa's chief prosecutor, who has led a spirited anti-corruption campaign against top South African politicians, has resigned, sparking allegations that he has been forced to quit by a political establishment fearful of his work.

Bulelani Ngcuka has overseen the prosecution of many influential people, including the anti-apartheid icon Winnie Mandela and Tony Yengeni, the former parliamentary chief whip of the ruling African National Congress. He also prosecuted top business people, most notably the arms dealer Schabir Shaik, who is also a private financial adviser to the Deputy President, Jacob Zuma.

His fearless work earned him many admirers, but the real trouble for Mr Ngcuka started when he took on Mr Zuma, over allegations that he had solicited bribes in an arms deal. Mr Ngcuka later said that he would not prosecute Mr Zuma, while insisting that there was a prima facie case against the Deputy President. Mr Ngcuka said the evidence was insufficient to secure a conviction, hence his decision, but his statement effectively scuttled Mr Zuma's chances of succeeding President Thabo Mbeki.

Mr Ngcuka's stance started a series of rows that saw Mr Zuma's supporters branding the chief prosecutor a former apartheid spy, but Mr Ngcuka was exonerated of all the accusations in January by a commission set up by Mr Mbeki to probe the allegation.

The finding provided little respite. Mr Ngcuka's enemies maintained the pressure and the prosecutor submitted his resignation letter to Mr Mbeki last week, although news of it broke only on Sunday.

Mr Mbeki has yet to accept the resignation of Mr Ngcuka. "Once the President has formally considered the matter ... a formal announcement will be made," a spokesman for the government said.

Political parties and analysts reacted with anger and said that Mr Ngcuka had been forced to resign for doing a good job. Sheila Camerer, spokeswoman for the main opposition Democratic Alliance, said: "Ngcuka was a tough minded crimebuster who played rough and acted without fear, favour or prejudice when pursuing criminals as required by the constitution, and therefore he was the right man for the job."

Tom Lodge, a political scientist at the University of Witwatersrandš and a prominent commentator, said that Mr Ngcuka's sudden departure did point to coercion. "This looks like the result of very effective political pressure," he told a local newspaper.