A statement released by the African National Congress, South Africa's dominant political party since Mandela's government ended racist apartheid laws after coming to power in 1994, labeled Trump the most "divisive, misogynistic and disrespectful person" ever to serve as U.S. president.
"All freedom-loving people of the world are appalled by these insults, which come from a person who himself is not a model of competent leadership," the party said, according to the Canadian Broadcasting Corporation (CBC).
"We do not believe that leaders who conduct themselves in the way Mr. Trump does are in a position to offer authoritative commentary on the life and work of Madiba," added the Nelson Mandela Foundation, using a term of endearment referring to the former president.
The condemnations came in response to excerpts from a book written by Michael Cohen, the president's longtime former personal attorney and fixer, who wrote that Trump accused Mandela of ruining South Africa after his death in 2013.
"Mandela f---ed the whole country up. Now it's a shithole. F--k Mandela. He was no leader," Trump said at the time, according to his former aide.
The White House has dismissed allegations raised by Cohen in the book, calling them the words of a disgruntled former associate seeking to clear his own name.