Deputy President Jacob Zuma should resign following the arms deal controversy in order to protect the dignity of his office before there are further humiliations, Democratic Alliance chief whip Douglas Gibson said on Sunday.

"The deputy president is fatally wounded and he should stand down. He surely has no prospect of succeeding to the Presidency and the ANC (African National Congress) will no doubt drop him at the next election.

"He should protect the dignity and the standing of his office by resigning now before there are further humiliations," Gibson said in a statement.

Public prosecutions head Bulelani Ngcuka announced on Saturday that Zuma would not be prosecuted over South Africa's multi-billion rand arms deal, despite indications that there may be a corruption case for him to answer to.

The decision was taken in spite of a recommendation by the investigating team that Zuma be criminally charged.

"We have concluded that, whilst there is a prima facie case of corruption against the deputy president, our prospects of success are not strong enough," he told reporters in Pretoria.

"That means that we are not sure if we have a winnable case. Accordingly, we have decided not to prosecute the deputy president."

Zuma has repeatedly rejected allegations that he tried to solicit a R500,000 bribe from Alain Thetard, the former southern African head of French arms company Thomson CSF.

The prosecuting authority has probed claims for the past two years of corruption flowing from the Nkobi Group's acquisition of shareholding in African Defence Systems (ADS), and Zuma's role therein.

Zuma's financial advisor Schabir Shaik was a director of the Nkobi group of companies, which had shares in Thomson CSF. Thomson, in turn, had shares in ADS.

Gibson said Ngcuka's decision not to prosecute Zuma did not lift the cloud of suspicion hanging over the deputy president's head.

"It will never be lifted because although there is a prima facie case against him, it will now not be tested in court."

Gibson said the matter was of over-riding public importance and he would approach the speaker for a debate when the National Assembly reassembled next week.

"South Africa is entitled to hear Parliament pronounce on the deputy president."

With acknowledgements to Sapa and the Weekend Argus.