Archbishop Emeritus Desmond Tutu on Monday called on President Jacob Zuma to reverse the appointment of national prosecutions boss Menzi Simelane, describing it as an "aberration".

"The appointment of advocate Menzi Simelane as National Director of Public Prosecutions (NDPP) is a setback for the integrity of South Africa's post-apartheid legal system," Tutu said in a statement.

"Simelane's integrity has been questioned from within his own political party and by his profession."

Tutu said a statutory commission, headed by senior African National Congress stalwart Frene Ginwala, deemed him unfit for the job.

Tutu was referring to the Ginwala commission of inquiry into whether Simelane's predecessor, Vusi Pikoli, was fit to hold office.

In her findings, Ginwala said it seemed that Simelane had tried to interfere in the National Prosecuting Authority (NPA) decision to arrest ex-top cop Jackie Selebi for corruption.

She came to this conclusion after Simelane testified at the hearings. But Justice Minister Jeff Radebe last week said Simelane was never given the opportunity to respond to Ginwala's accusations.

However, Tutu said the government's ignoring of Ginwala's finding "besmirches the office of the NDPP."

"The appointment of one whose ready willingness to act on political instructions has been questioned by a statutory commission does nothing for people's confidence in the law," said Tutu.

The Pretoria Bar Council is currently investigating a complaint against Simelane, related to his appointed as NDPP despite the Ginwala commission findings.

Tutu said: "To witness the professional body of South African advocates - Simelane's peers - considering disbarring him is a national embarrassment. This distresses me deeply."

He said he had raised his objections with Radebe and Deputy President Kgalema Motlanthe while Zuma was out of the country.

"I now appeal to President Zuma to do the right thing. Since his appointment, he has done much to restore the confidence of South Africans in government. But the appointment of advocate Simelane is an aberration.

"The appointment should be reversed," said Tutu.