Cape Town - Former chief prosecutor Mokotedi Mpshe insisted on Tuesday it was not his decision to delay the prosecution of President Jacob Zuma.“I wish to reaffirm that as far as I was concerned, I did not have the legal authority to institute proceedings against Zuma,” the former head of the National Prosecuting Authority (NPA) said in an affidavit filed in the DA spy tapes matter.“Consequently I did not take the decision to charge Zuma, nor did I take the decision to delay the prosecution.”The spy tapes saga refers to the opposition DA's court application to have the decision not to prosecute Zuma reviewed.Mpshe's affidavit, that was signed on Tuesday, could be considered a major boost for the NPA and Zuma, who are defending the decision to withdraw the charges against him.The DA's application follows its eventual receipt of the so-called "spy tapes", which they believe contain enough information to proceed with a review application of the decision to drop corruption charges against Zuma.The DA was handed the spy tapes last year after the Supreme Court of Appeal ruled that the NPA had to comply with a previous order to release the tapes. Zuma opposed the move. The tapes, containing recorded phone conversations, allegedly revealed collusion between the former head of the directorate of special operations - the now defunct Scorpions - Leonard McCarthy, and the NPA's former head Bulelani Ngcuka to manipulate the prosecution of Zuma before the ANC's Polokwane conference in 2007.The charges related to Zuma allegedly receiving a bribe from an arms company via his former financial adviser Schabir Shaik, who was convicted of corruption and is currently on medical parole.Zuma was elected ANC president at the 2007 conference. Former president Thabo Mbeki had been a contender for a second term and the contest for the top position caused rifts in the party. The Scorpions were also disbanded.The corruption charges were dropped shortly before Zuma was sworn in as president in 2009.At the time, Mpshe claimed the tapes revealed a political conspiracy against Zuma and so the case could not continue.With Mpshe now confirming that McCarthy played a central role in Zuma's prosecution, it strengthens the NPA and Zuma's arguments that McCarthy abused his power as prosecutor to favour Mbeki in the leadership race at the time.The NPA and Zuma have also argued that it was McCarthy's decision to postpone the prosecution until after the ANC's Polokwane conference - and this has now also been confirmed by Mpshe in his affidavit.Both Zuma and the NPA consider this to be proof that McCarthy interfered with the prosecution.The DA hopes that the matter would be heard by the High Court in Pretoria before September.