Thuli Madonsela said it was “unethical and unlawful” to publish her report.
According to the Mail and Guardian, Thuli Madonsela said President Jacob Zuma had derived “substantial benefits” from the upgrade.
The government says the improvements were needed for national security.
It has gone to court to block publication of Thuli Madonsela’s report.
Last week, several newspapers defied a government warning not to publish photographs of the residence in Nkandla.
Opposition parties have condemned it as a waste of public money, while the governing ANC says it believes he has done nothing wrong.
Jacob Zuma’s office has declined to comment on the Mail and Guardian article.
The newspaper says it has had “direct access” to the provisional report by Thuli Madonsela, the public protector.
It said the upgrades included a visitors’ lounge, amphitheatre, cattle enclosure, swimming pool and houses for the president’s relatives.
The newspaper said it published the article because “all the evidence points to a systematic attempt by the government to shield disclosures about the scandal from public view”.
“There are good reasons for fearing that the security ministers who tried to interdict Madonsela earlier this month may be planning further litigation to block its release,” it said.
Thuli Madonsela has distanced herself from the article and the quotes that have been attributed to her, saying that the final report would be released in about a month.
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