South Africa's controversial chief prosecutor has handed in his letter of resignation, after leading a tough anti-corruption drive.
After 10 year, Ngcuka felt it was time to move on
Bulelani Ngcuka has been at the centre of a political storm for the past year after implicating Vice-President Jacob Zuma in a corruption scandal.
But Mr Ngcuka's spokesman denied reports that he had come under government pressure to stand down.
President Thabo Mbeki has not yet said whether he will accept the resignation.
"It was not pressure but it was in the interests of the organisation," Sipho Ngwema - Mr Ngcuka's spokesman - told the BBC's Network Africa programme.
He said that after 10 years as director of public prosecutions, Mr Ngcuka felt it was time to move on.
Unknown in 1994
Pledged to fight corruption
Secured conviction of Winnie Mandela
Accused of spying for apartheid
"For his personal growth, he has to look elsewhere, for other challenges," he said.
But opposition Democratic Alliance spokeswoman Sheila Camerer said Mr Ngcuka had come under huge pressure.
"Ngcuka was a tough-minded crime-buster 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," she said.
Mr Ngcuka last year announced there was prima facie evidence to suspect Mr Zuma of corruption in a multi-million dollar arms deal, but not enough to prosecute him.
Mr Zuma, a favourite to succeed Mr Mbeki, angrily responded that his reputation was being tarnished, but he was not being given the opportunity to clear his name in court.
Shortly after Mr Ngcuka's allegations about Mr Zuma, South African media reported that he had been an apartheid spy.
A presidential commission of inquiry was set up, which exonerated him.