Former chief prosecutor Bulelani Ngcuka has sought to rebut allegations levelled against him by ex-top cop Jackie Selebi in court on Monday.

Ngcuka denied plotting against Selebi as Jaap Cilliers, for Selebi, contended in a plea explanation.

"I reject all these allegations with contempt," Ngcuka said in a statement issued by his spokesman, Sipho Ngwema.

The charges of corruption and defeating the ends of justice against Selebi relate to payments he allegedly received from ex-Hyundai boss and mining businessman Billy Rautenbach, slain mining magnate Brett Kebble and his associate Glenn Agliotti, a convicted drug trafficker who is also accused of murdering Kebble.

The State, in papers before the court, alleged that "Agliotti and/or Kebble and or Rautenbach and/or the relevant corporate entities have benefited the accused in the period 1 January 2000 up to and including 31 December 2005... in an amount of at least but not restricted to R1,2-million."

Cilliers said in court that Ngcuka and his successor, Vusi Pikoli, had plotted against Selebi while they allegedly let dangerous criminals off the hook "in exchange for false statements against the accused".

These alleged criminals apparently included Rautenbach, who is on the State's witness list.

In the lengthy statement, Ngcuka said he would ordinarily ignore such allegations which are aimed at "creating a sideshow".

"In this instance, however, I have reluctantly decided to respond to the allegations as they emanate from a very senior former law enforcement officer," said Ngcuka.

"If Mr Selebi, or anyone else, has evidence of my criminal involvement, they may present it in court."

Ngcuka was not on the witness list for Selebi's corruption trial in the High Court in Johannesburg, said Ngwema.

"He is not a witness... he has nothing to contribute with that case," Ngwema told Sapa.