The National Prosucting Authority (NPA) still needs to investigate further before it will decide whether or not to prosecute President Jacob Zuma for corruption relating to Nkandla, the Democratic Alliance (DA) said on Monday.

This was the response DA leader Mmusi Maimane received to his letter last week, in which he called on National Director of Public Prosecutions (NDPP), Shaun Abrahams, to explain if he would prosecute Zuma or not.

"In a responding letter, the acting special director of public prosecutions, Advocate M Govender, refused to give a simple answer as to whether the President will be prosecuted or not, even though the completed investigation has been with the National Prosecuting Authority (NPA) for almost two years now," Maimane said in a statement on Monday evening.

Previously, the minister of police told Maimane in a written reply to a parliamentary question that the investigation had been concluded and that the docket was handed to the NDPP on August 21, 2015 for a decision on prosecution.

"Advocate Govender now claims that further investigation is required before he can arrive at a decision. This is completely unacceptable and smacks of a justice system using every stalling tactic in the book to avoid prosecuting Jacob Zuma for his unlawful actions," said Maimane.

He intended writing to Justice Minister Michael Masutha asking him to see to it that a decision was made, failing which the DA would approach a court to compel the NPA to make a decision.

"The selective prosecution on the part of the NPA is a violation of its duty to prosecute without fear, favour or prejudice."

Maimane said Abrahams was required to prosecute anyone who had a case to answer for, even if that person happened to be the head of state.

Earlier on Monday, NPA spokesperson Luvuyo Mfaku said they would reply to the DA's lawyers. He said this was confidential.

Maimane laid the charges of corruption at the Nkandla police station, near Zuma's homestead, in March 2014, when he was still DA spokesperson. This followed the release of former public protector Thuli Madonsela’s Secure in Comfort report. She found Zuma “unduly benefited from the enormous capital investment” in so-called security upgrades, costing R246-million, to his homestead.

In March last year, the Constitutional Court ruled that Zuma failed to uphold the Constitution when he ignored Madonsela’s recommendations that he repay money spent on upgrades not related to security. Zuma did this with the help of a loan after Treasury determined he had to pay R7.8-million.

Last week, Public Works Minister Nathi Nhleko, who is the former police minister, said the NPA decided not to institute criminal proceedings against three officials implicated in the Special Investigating Unit's report on Nkandla.