Zuma had asked Madonsela to delay reporting her findings until he has reviewed any evidence that implicated him
Public Protector Thuli Madonsela was due on Friday to release her preliminary findings in a probe into the Guptas, an Indian-born family accused of using their close ties with Zuma to influence cabinet appointments.
"I can confirm that the president has applied for a court interdict," Zuma's spokesman Bongani Ngqulunga told Reuters.
Madonsela questioned Zuma for four hours last week as part of her final investigation before her seven-year term comes to an end on Saturday.
In a statement late Thursday, graft watchdog spokeswoman Kgalalelo Masibi said Madonsela would release her last batch of investigation reports on Friday and provide updates on the progress of other investigations. But she did not state whether the report on the Guptas would be among them.
Although Zuma and the Guptas deny wrongdoing, the allegations have damaged the president, who was separately forced to repay part of the cost of a lavish upgrade to his private residence as a result of an investigation by Madonsela.
On Monday, Zuma asked Madonsela not to report her findings until he has had a chance to question other witnesses and reviewed any evidence that implicated him. But Madonsela said the president had been given all the evidence implicating him on Oct. 1, and urged Zuma to answer questions to aid the probe.
The main opposition Democratic Alliance party said in a statement that Zuma was "worried about what is contained in this report, and desperate to stop it from being made public".
Lawyer Gert van der Merwe, who represents Ajay Gupta, said his client would not seek to block the report.
The row over the report adds to pressure on Zuma, whose government was rocked this week when prosecutors ordered Finance Minister Pravin Gordhan to appear in court on Nov. 2 to hear fraud charges against him, news that sent markets reeling.
Analysts have said that Gordhan has been a target of political pressure from a faction allied to the president although he has denied any rift with the finance minister.
Perceived divisions between Gordhan and Zuma have previously rattled markets in Africa's most industrialised economy, which is at risk of having its credit rating downgraded to "junk" later this year.
The premier of Guateng, South Africa's most economically important province, said the fraud charges levelled against Gordhan were frivolous and undermined efforts to avoid a ratings cut.
"It undermines every little effort that South Africa is making to move forward," David Makhura said at a Thomson Reuters conference in Cape Town, accusing Zuma's administration of "recklessness".