Assange said The Guardian's reporter "chosen to receive the information (about the rape allegations) was a known critic of our organization.
"The Guardian didn't ask why these documents were made available before a court hearing. What were the motives? These are questions that haven't been answered," Assange told the daily.
A week ago, The Guardian printed details of the Swedish rape and sexual molestation inquiry against Assange, saying it had access to documents relating to the case. It denied allegations made by Assange elsewhere that it had selectively published sections of the documents.
Assange argued that he and other individuals should not be held to the same standard his whistleblowing website leveled at governments and officials whose secrets WikiLeaks is revealing.
"Transparency is for governments. Not for individuals. The aim of revealing information about powerful people is to make them responsible. When a government gives legal material to a newspaper to prejudice someone, that is an abuse," he said in the interview, published in Portuguese.
AFP inquiries to Estado de Sao Paulo and to WikiLeaks about the interview were not immediately answered.
The Guardian is one of several newspapers around the world working with WikiLeaks to publish thousands of US diplomatic cables revealing embarrassing interactions and observations by US embassy staff and the US State Department.
In his interview with Estado de Sao Paulo, Assange said US government actions against him since WikiLeaks started publishing the US diplomatic cables "was akin to the McCarthyist period," when supposed Communist sympathizers were hounded by US officials in the 1950s.
He also said the United States was applying pressure "on allied countries such as Australia, Britain and Sweden to spy on me and prosecute me."
Assange said WikiLeaks was poised to reveal further information "that would have a big political impact on the US government and other governments." As in other interviews he has made, he declined to elaborate.
There were also "thousands and thousands" of other documents, including "on banks in Switzerland, Iceland, the Cayman Islands, the United States and Britain" in WikiLeaks's possession, he said.