President Jacob Zuma had acted in terms of the law in extending the term of office of Chief Justice Sandile Ngcobo, his spokesperson Mac Maharaj said on Thursday.

"Comments that he acted unlawfully and outside the Constitution of the Republic of South Africa are false," Maharaj said.

Zuma had acted in terms of Section 176(1) of the Constitution which "provides for the extension of the terms of office of judges as well as Section 8(a) and (b) of the Judges' Remuneration and Conditions of Employment Act of 2001 which authorises the President to request the Chief Justice and the President of the Supreme Court of Appeal to continue to perform active service, from the date on which they are eligible to be discharged from active service, for a period determined by the President".

The Act was passed unanimously by both Houses of Parliament 10 years ago, after careful consideration.

"Nobody complained about the law until the President used it to extend the term of Chief Justice Ngcobo."

On Wednesday, Zuma accepted Ngcobo's withdrawal of his acceptance of the extension of his term of office which expires on August 14.

"The President respects and understands the Chief Justice's decision. He will soon appoint a new Chief Justice in terms of his powers as set out in the Constitution," Maharaj said.

But, constitutional expert Pierre de Vos said the section of the Act on which Zuma had relied was "almost certainly unconstitutional".

Writing on his blog site "Constitutionally Speaking", De Vos said the inevitable controversy that resulted from this move threatened the integrity of both the office of the Chief Justice and the person of the incumbent.

"The government made things worse by refusing to admit that the section on which the president had relied might be constitutionally problematic, and by then trying to play party politics with the extension by suggesting that those who were challenging the constitutionality of section 8(a) were motivated by a hatred for the Chief Justice."

With the issue having been politicised and personalised, Ngcobo was placed an in almost impossible situation.

The government's original intransigent stance had threatened to destroy the integrity of a judge who has served South Africa with distinction.

"By then – belatedly – proposing an amendment to the Act that would only extend the term of office of the Chief Justice and the President of the Supreme Court of Appeal (SCA), Justice Minister [Jeff Radebe] further complicated matters as it was far from clear that this new proposal would pass constitutional muster."

De Vos questioned why the justice minister and the president had not thought, a year or two ago, whether section 8(a) was constitutional, and what other legal mechanism could be used to extend the term of the Chief Justice.

"How can one govern a country when one does things at the last minute in the hope that one can bluster one's way through by denigrating those who insist on upholding the Constitution?"