South African President Jacob Zuma has taken steps to prevent the release of a report into the alleged political interference by him and his supporters.
The public protector is due to release her preliminary findings on Friday.
She has been examining allegations that Mr Zuma allowed a business family undue influence over his administration.
The president denies any wrongdoing. In March a court ruled that he had failed to repay taxpayers' money used to upgrade his private residence.
"I can confirm that the president has applied for a court interdict," Mr Zuma's spokesman Bongani Ngqulunga told the Reuters news agency on Thursday.
Ms Madonsela questioned Mr Zuma for four hours last week as part of her final investigation before her seven-year term tenure as public protector concludes this weekend.
She has been hailed for her diligent work exposing official misconduct, including allegations that the president used taxpayers' money to build a cattle enclosure, amphitheatre, swimming pool, visitor centre and chicken run at his home in Nkandla.
South African media has quoted sources within Ms Madonsela's office as saying that her latest report cannot be released until a court has made an order in relation to Mr Zuma's request for it to be blocked.
The focus of her probe is on the Indian-born Gupta family, who are accused of using their close links with Mr Zuma to influence cabinet appointments.
Although Mr Zuma and the Guptas insist they are innocent, correspondents say the allegations will do little to improve the tarnished reputation of the president, who was forced to repay part of the cost of the lavish upgrade to his private residence because of Ms Madonsela's inquiries.
On Monday, Mr Zuma asked her not to report her findings until he has been given an opportunity to question witnesses and review any evidence that implicates him.
Ms Madonsela argues the president was supplied with all the evidence he needs earlier this month and has urged him fully to co-operate with her inquiry.
The main opposition Democratic Alliance party for its part argues that Mr Zuma is "worried about what is contained in this report, and desperate to stop it from being made public".
The latest row adds to the pressure on Mr Zuma, whose government was reeling this week when prosecutors ordered Finance Minister Pravin Gordhan to appear in court in early November to face fraud charges.
He denies any wrongdoing and says the charges are politically motivated.