President Thabo Mbeki is to face his first grilling in parliament tomorrow on the political dogfight between National Director of Public Prosecutions Bulelani Ngcuka and Deputy President Jacob Zuma.

But the president is not expected to announce any action in relation to Zuma or Ngcuka and is unlikely to say anything that could be construed as taking sides in what he insists is a matter for the judicial process.

Mbeki is to be challenged by Democratic Alliance (DA) leader Tony Leon to say whether he has asked or intends to ask the deputy president to stand down until the allegations of corruption against him have been refuted and he has been exonerated.

But Mbeki is not expected to depart from an earlier response - in which he insisted he was not becoming involved in the controversy - given to a question put to him by Independent Newspapers at a media briefing in Pretoria on July 29.

"You cannot help forming a judgment once you (become involved)," Mbeki said.

On that occasion he called for a swift resolution of the investigation into allegations that Zuma was the "JZ" referred to in a French arms company's memo about making payments in return for "protection".

Two weeks later, Ngcuka said the investigation had been suspended and Zuma would not be prosecuted although there was prima facie evidence of corruption against him.

As the immediate threat of investigation had been removed, it became less likely that Mbeki would intervene. Mbeki is likely to make the point, as Justice Minister Penuell Maduna has done, that because Zuma has not been charged the question of political intervention - to persuade him to step down until the allegations against him have been tested - falls away.

Mbeki is also likely to stay well clear of the subject of the frenzied allegations that Ngcuka was an apartheid spy and to cite the convening by Maduna of a cabinet committee to look into all aspects of the claims as well as the mandates of the crack Scorpions unit and the police and whether there are tensions between them.

There are misgivings in some senior ANC circles about Ngcuka's using the term "prima facie", which has a specific legal meaning.

"I think he was using it in a looser, more colloquial sense," said one ANC source, "and that was unfortunate."

Mbeki is likely to oppose vigorously any suggestion that Ngcuka should stand down because of the spy allegations.

In the National Council of Provinces (NCOP) last week, Zuma adopted a defiant stand and flatly refused to stand down as deputy president or as head of the moral regeneration campaign.

The ruling ANC, which is deeply divided over the spy allegations against Ngcuka, has studiously avoided taking a position on Zuma's future.

Mbeki faces six questions tomorrow on the Zuma-Ngcuka matter and on the deteriorating human rights situation in Zimbabwe. It is likely to be a lively session, with members allowed to ask 24 follow-up questions in all.

With acknowledgements to John Battersby and the Cape Times.