In its legal battle with ANC deputy president Jacob Zuma, the National Prosecuting Authority (NPA) has questioned Public Protector Lawrence Mushwana's integrity, powers and jurisdiction.

This relates to Mushwana's finding that former head of prosecutions Bulelani Ngcuka violated Zuma's rights.

Head of the Scorpions Leonard McCarthy filed an affidavit yesterday to caution Zuma - who is facing a corruption charge - that he should not rely on Mushwana's 2004 report to defend himself and his constitutional rights because the public protector's report was riddled with inaccuracies and flaws. Zuma has repeatedly cited Mushwana's report, saying his rights were violated by the NPA.

In 2004, the NPA tried to respond to the report but was asked - it is believed, by a senior member of the government - not to do so, to avoid embarrassing Mushwana and to minimise tension between the two institutions.

The NPA's response was not made public, to protect the office of the public protector.

Mushwana had concluded that Ngcuka violated Zuma's rights when he publicly pronounced that there was prima facie evidence of corruption against the country's then-deputy president, but that the case was not winnable and he would not be prosecuted.

The NPA yesterday invoked its 2004 response to Mushwana's report in an attempt to demonstrate to Zuma that the public protector's powers, integrity, ability to interpret the law and jurisdiction were open to question.

The NPA's response - a joint statement by Ngcuka and then-justice minister Penuell Maduna - said no one but the courts had the right to question their decisions and that Mushwana had violated this principle.

"Since the NPA is, in terms of its functions and its powers, subject only to the Constitution and the law, no other institution can question or review such decisions, except the courts. Any person who is dissatisfied with a decision in this regard can have it reviewed by the courts … The public protector therefore does not have the power to review or question such a decision," read the NPA's response.

It said, although Mushwana's report created an impression that he was careful not to question or review Ngcuka's decision, "this is in fact what transpired".

"He goes further and reviews the decision of the national director, and in his observations and findings he seeks to substitute the discretion that vests in the national director in law," said the NPA response, which is now part of the State affidavit in the Zuma trial, due to resume in Pietermaritzburg next week.

With acknowledgements to Moshoeshoe Monare and Cape Times.