Justice Minister Penuell Maduna on Tuesday defended National Director of Public Prosecutions Bulelani Ngcuka's decision not to prosecute Deputy President Jacob Zuma, while opposition parties renewed their calls for Zuma to step down.

At the same time, Home Affairs Minister Mangosuthu Buthelezi said the Scorpions should have gone through with the prosecution, as it appeared Zuma had been unfairly "tried by media".

Speaking in Kimberley after opening a new centre for rape victims, Maduna said the decision not to prosecute Zuma was not the first or last of its kind.

The National Directorate of Public Prosecutions regularly decided not to prosecute alleged offenders, despite prima facie evidence against them.

"You don't prosecute people just for the sake of prosecution, he said.

"Once a prima facie case has been established, you consider the prospects of success and other things before deciding to prosecute.

"A prima facie case does not necessarily constitute proof beyond reasonable doubt in a court of law," Maduna said.

At a weekend media conference, Ngcuka said Zuma would not be prosecuted, despite indications that there may be a corruption case for him to answer.

Buthelezi, addressing a Johannesburg Press Club lunch said: "I think the way the Zuma saga has been handled has not been fair. I agree he has been tried by the media."

"The judicial process ensures the right of each man to have his day in court."

To say there was a prima facie case, but not enough evidence for a conviction, was "talking from both sides of your mouth", Buthelezi said.

Zuma again proclaimed his innocence on Tuesday.

"The Presidency has noted the media reports relating to the charge sheet of (businessman and Zuma's financial advisor) Mr Schabir Shaik and references made in it relating to the deputy president's financial affairs," his office said in a statement.

The allegations made in the charge sheet were still to be tested in court when the matter goes to trial.

"The deputy president wishes to reiterate that he is not guilty of any wrongdoing or corruption, either relating to the arms deal or his financial affairs," the statement said.

Democratic Alliance leader Tony Leon told journalists at Parliament that on the face of the evidence against him, Zuma should step down "or be ordered to do so".

According to media reports, the State is alleging that Shaik paid Zuma nearly R1,2-million between 1995 and last year, and took elaborate steps to hide the origin of most of the payments.

It is also alleged that most payments can be traced back to arms deal beneficiaries.

The charge sheet was handed to Shaik in the Durban Regional Court on Monday.

Shaik was released on bail of R1 000, and the case postponed to October 3.

Leon said based on Zuma's own version of events, Zuma was obliged and compelled to issue legal process against Ngcuka. If he did not sue for defamation, he was acknowledging the veracity of Ngcuka's claims, Leon said.

On the other hand, if Zuma did sue, South Africa would have the unprecedented situation of the second highest official in government launching a legal process against government's chief prosecuting arm. This would be intolerable.

"The only solution is for Deputy President Zuma to step down. If he fails to do so, President (Thabo) Mbeki must take charge and order him to resign."

United Democratic Movement leader Bantu Holomisa said in a statement that now that the charge sheet was public knowledge, nobody could doubt the depth or scope of the alleged criminal activities that reflected directly on Zuma.

"It is clear from these charges that it was only the status of his office that has thus far saved Mr Zuma the embarrassment of being arrested and charged.

"Mr Zuma must go immediately. He must resign or be fired to await the outcome outside government office," Holomisa said.

The Independent Democrats (ID) had asked Ngcuka to confirm in writing the decision not to prosecute Zuma, and the reasons for this, the newly-formed party said in a statement.

If this did not happen by September 1, the ID would "constitute legal proceedings".

In a separate statement, the Azanian People's Organisation (Azapo) called for Zuma to take leave from his duties until such time as all allegations against him had been cleared.

With acknowledgements to Sapa and the Mail & Guardian.