The 350-page report on corruption was compiled by Thulisile Madonsela, the former public protector, who is effectively the country’s anticorruption czar. Ms. Madonsela, who was in the courtroom on Wednesday, told reporters, “An allegation that the state has been captured in the interests of the president and his friends is an allegation that needs to be investigated.”
In her report, released in November 2016, Ms. Madonsela called for the creation of a public inquiry, but Mr. Zuma has resisted, saying that the public protector did not have the authority to order him to set up the inquiry since the decision was his prerogative.
Judge Mlambo, however, said that the accusations “detailed in the report are extremely serious,” and that Mr. Zuma had a “clear personal interest in the outcome of the inquiry,” according to local news media reports. The judge also said Mr. Zuma should pay the costs of challenging the accusations.
Judge Mlambo ordered Mr. Zuma to set up the inquiry within 30 days, ensure that its work concluded within 180 days and inform Parliament within 14 days of the findings. It was not immediately clear whether Mr. Zuma would appeal the order.
The court’s ruling came at a delicate time in the often-opaque maneuverings of the African National Congress, which has governed South Africa since the election in 1994 of Nelson Mandela as the nation’s first black president in the post-apartheid era.
Traditionally, the party chooses its officials at an elective conference, and the person picked as its leader is the overwhelming favorite to be its presidential candidate in the next national elections, due in 2019.
The conference starts on Saturday, and the front-runners include Nkosazana Dlamini-Zuma, a former government minister and Mr. Zuma’s ex-wife; and Cyril Ramaphosa, a former mineworkers’ union leader who ranks among the wealthiest people in the country.
The court ruling on Wednesday may well deepen sentiment among A.N.C. officials that it is time for a clear break with Mr. Zuma, even though he is scheduled to remain in office as president until 2019, despite an accumulation of corruption-related crises.
In August, he survived a no-confidence vote in Parliament by a far more slender margin than analysts had expected. The 177-198 vote in his favor, with nine abstentions, was taken as a sign that accusations of corruption and ineptitude had jeopardized the party’s hold on power.
In October, the Supreme Court of Appeal upheld a lower court’s reinstatement of nearly 800 corruption charges against Mr. Zuma relating to an arms deal before he became president, in 2009.
On Friday, the High Court ordered the removal of a chief prosecutor appointed by, and seen as favorable to, Mr. Zuma. The court also said the prosecutor’s replacement should be named by Mr. Ramaphosa, since the president himself was “conflicted.”