The ANC’s national communications manager, Khusela Sangoni, said the party had not sent anyone death threats and Mabulu should prove his allegations.
“Ayanda is looking for attention, he should name the person,” she said.
Mabulu has come under fire for the piece.
He said since unveiling the painting on Thursday, he had been receiving phone calls from unknown numbers threatening his life.
“That’s a way of silencing me,” he said.
“I don’t have boundaries when it comes to creating art, I am a free human being.”
He said that the reason he had not reported the death threats was because he was not intimidated by anyone.
Mabulu is widely known for creating controversial art interpretations of the country’s political woes.
In 2015 he painted the Spear Down My Throat (The Pornography of Power) which shows Zuma with his penis in the throat of a woman (representing South Africa) while she is being penetrated by a hyena in a suit.
Last year he painted Zuma performing a sex act with controversial businessman Atul Gupta.
The latest painting shows Zuma raping Mandela’s legacy.
He said his works talks about “the current situation the country is in”.
“Hopefully people can see the bigger picture of what I created,” he said.
This week the Nelson Mandela Foundation noted the work, saying they respected Mabulu’s freedom of expression however, they described the work as “distasteful”.
Mabulu said he has no regrets using Mandela in the picture.
The ANC said it found “his work grotesque, inflammatory and of bad taste.”
Art critics have criticised Mabula’s latest artwork as “porn”.
Media expert Dr Musawenkosi Ndlovu said although Mabulu is protected by the constitution he can face a legal challenge.
“He can face a legal challenge, The question is whether the person challenging him can or cannot win.
“It makes it very difficult for the courts to tell an artist what and what not to do,”he said.
Mabulu’s work, standing at 2.3 meters by 1.7m, has been collecting dust at his studio in Fordsburg, Johannesburg.
“No gallery has approached me and the work is not on exhibition, but I am looking for alternative spaces to showcase the work.”