The elite Scorpions unit has steadfastly refused to confirm or deny that it is investigating Deputy President Jacob Zuma.

Despite widespread publication in the press of the details of a Scorpions affidavit that has been submitted to the Durban High Court and which points clearly to an investigation into Zuma, the unit has remained adamant that it does not name people under investigation. The details suggest Zuma was named in negotiations for payment in exchange for protection for a French company that won a contract under the arms deal.

"In terms of our policy, we have never confirmed or denied that we are investigating anyone, including the deputy president, and we don't intend to change that policy," Scorpions spokesman Sipho Ngwema said.

Zuma has reportedly been irritated that the Scorpions have not questioned him about the allegations.

Speaking at the ANC's national conference on Tuesday, President Thabo Mbeki defended Zuma's right to remain deputy president as long as formal charges had not been laid against him.

The ANC's secretary-general, Kgalema Motlanthe, said yesterday he understood the Scorpions' stand on publicising their investigations. The Scorpions would "have to decide at what point they make them public".

Publicising their investigations "could jeopardise their work or cast aspersions or doubts on an innocent person", he said.

"Allegations, until proven, remain allegations - that's why there's always sensitivity about investigations."

The Scorpions were confronted with the "difficulty" of announcing an investigation and finding "that you may not be able to gather enough evidence to make a case".

Motlanthe agreed that the Scorpions could find themselves in a precarious situation if they laid charges against Zuma, prompting him to step down, only to find they could not prove their case in court.

"That is a fair view," Motlanthe said.

"They have to consider all possibilities of the implications of whatever step they take - they carry that responsibility."

Meanwhile, the Democratic Alliance (DA) told Sapa yesterday that by ignoring its call for an inquiry into the allegations against Zuma, Mbeki had created the impression that the ANC had much to hide.

Mbeki's comment that there was no need for Zuma to step down was misguided, DA spokeswoman Raenette Taljaard said. "No one has called for the deputy president to step down until such time as allegations against him have been proven and he has been charged."

Far more serious was Mbeki's failure to respond to the DA's request that he appoint a commission to investigate the allegations against Zuma.

"A letter from the president's office merely acknowledged receipt of the request and stated that the matter had been brought to the president's attention," Taljaard said.

"His disdain for opposition and his attempts to vilify the DA aside, this remains an inadequate response from the head of state to a formal request by the official opposition - an opposition asserting its rightful role in what should be an open democratic society."

With acknowledgements to Jeremy Michaels and Cape Times.