There was "sufficient evidence" on the so-called spy tapes for a review application of the decision to withdraw corruption charges against President Jacob Zuma, Democratic Alliance (DA) leader Helen Zille said on Monday.

"I have read the transcripts of the tapes handed to us by the NPA [National Prosecuting Authority] last Thursday. They constitute recordings of 36 conversations over 5 months," Zille said in her DA SA Today newsletter.

"Without revealing the contents, I am satisfied that the 'spy tapes' provide sufficient evidence to continue our review application of the decision, by the then acting National Director of Public Prosecutions, Mokotedi Mpshe, to withdraw the charges against President Zuma."

However, the DA has been advised by its laywers not to make the content public.

"And while I believe that it would be in the public interest to release these records, the DA's legal team has advised that the 'discovered documents', including the recordings, may only be revealed during the court proceedings for which they were required," said Zille.

The DA was handed the spy tapes last week.

This followed the Supreme Court of Appeal ruling that the NPA had to comply with a previous order to release the tapes. Zuma had opposed the move.

The recordings, internal memoranda, reports and minutes of meetings dealing with the contents of the recordings had to be provided.

The tapes, containing recorded phone conversations, allegedly reveal collusion between the former heads of the Directorate of Special Operations, the now defunct Scorpions, Leonard McCarthy, and the NPA's former head Bulelani Ngcuka, to manipulate the prosecutorial process before the ANC's Polokwane conference in 2007. Zuma was elected African National Congress president at the conference. Former president Thabo Mbeki had been a contender for another term.

At the time, acting NPA boss Mokotedi Mpshe said they showed there was a political conspiracy against Zuma and so the case against him could not continue. The charges were dropped shortly before Zuma was sworn in as president in 2009.