In a scathing ruling, five Supreme Court of Appeal judges have lashed out at what they condemned as the cavalier way in which President Jacob Zuma appointed the national director of public prosecutions.

Two years after Zuma appointed Menzi Simelane, an advocate, to head the country's prosecuting authority, the court found that Simelane's appointment was invalid, and should be reviewed and set aside because it was ''inconsistent with the constitution".

Simelane's tenure now hangs in the balance.

The court flayed Zuma, saying it was clear that he had not made adequate inquiries before appointing Simelane.

In his judgment, Judge Mohammed Navsa said: "I accept that the president must have a multitude of daily duties and is a very busy man. However, when he is dealing with an office as important as that of the national director of public prosecutions then time should be taken to get it right.

"On the available evidence, the president could not have reached a conclusion favourable to Simelane, as there were too many questions concerning his integrity and experience."

But Simelane's job seems safe for now, pending a review by the Constitutional Court. Justice Department spokesman Tlali Tlali said the department was "disappointed" that the ruling was not in its favour. He said replacing Simelane could not "be entertained" at this stage.

The Presidency was not available for comment.

The Times understands that Simelane had long lost favour with Zuma, who was, ironically, waiting for the court's ruling before removing him.

NPA insiders said recent incidents involving Simelane and the undermining of his authority had fuelled speculation within the organisation that he would be the next to get the boot. Willie Hofmeyr was removed as Special Investigating Unit head this week.

Earlier this month, Zuma disregarded Simelane's recommendation that Michelle Ramoothy be appointed special director of the Specialised Commercial Crimes Unit, instead giving the job to Lawrence Mrwebi.

And last month Simelane was not invited to the opening of a court in Bloemfontein. Instead, Nomgcobo Jiba, a Zuma appointee who was once suspended from the NPA for allegedly leading a conspiracy against a colleague - was invited as a special guest.

Ruling on an application brought by the DA, the Supreme Court of Appeal judges found that both Zuma and Justice Minister Jeff Radebe had made material errors of fact and law in the process leading up to Simelane's appointment in November 2009.

Central to the DA's case was that Simelane was not suitably qualified for the position, and that he was not a fit and proper person for the job "with due regard to his experience, conscientiousness and integrity".

The DA based its case on what it termed Simelane's "misleading and untruthful evidence" during the 2008 Ginwala Inquiry.

The Ginwala Commission was set up to establish the fitness to hold office of Simelane's predecessor, Vusi Pikoli.

Simelane's lack of integrity, argued the DA, would result in his not being able to perform his duties without fear or favour.

A fundamental problem for Zuma and Radebe, ruled the judges, was that they considered the Ginwala report irrelevant, based on the rigid view that the inquiry into Pikoli's fitness for office did not concern Simelane's integrity.

The DA pointed out that, when he was president, Kgalema Motlanthe used the Ginwala Inquiry's minor criticisms of Pikoli to remove him from office, but when it suited Zuma the inquiry's "trenchant" criticism of Simelane was ignored.

Just 38 when appointed to head the NPA, Simelane had practised as an advocate for only two years. He had held positions at the Competition Commission and the Department of Justice - neither of which involved court work, nor investigations and prosecutions.

The DA said Simelane had served the NPA for only about six weeks as one of four deputies and had "extremely limited experience". His CV was shoddily prepared and was full of spelling and other errors.

NPA spokesman Mthunzi Mhaga said he could not comment.