Former Public Protector Thuli Madonsela says Duduzane Zuma lied to the state capture commission of inquiry when he testified that she had failed to give him the opportunity to respond to damaging state capture claims against him, Business Day reported.
Madonsela reportedly said that investigators had even offered to travel to Dubai to speak to him.
But on Monday, Zuma said he was never given right of reply, News24 reported.
"This is the first time I am being asked these questions. I was not given an opportunity by the Public Protector," Zuma told the commission.
According to The Citizen, Madonsela said Zuma was given numerous opportunities to respond to the allegations before the report was released, from as early as the beginning of September 2016.
"He's lying and I don't know why," Madonsela reportedly said.
Duduzane, the son of former president Jacob Zuma, is a business partner of the Gupta family.
The Guptas are accused of capturing key officials within the Zuma administration and of running a parallel government designed to advance their businesses, with Zuma ceding much of his power, including that to fire and hire ministers, to them, Business Day reported.
When Madonsela's team reportedly made contact with Zuma telephonically to set up an interview in early September 2016, he stated that he was out of the country and would indicate when he was available, she said, according to The Citizen.
Later, in September 2016, around the time Zuma supposedly was on a business trip to Dubai, he was reportedly contacted and offered an opportunity to communicate via Skype, but he declined this because he said his lawyer would not be available.
Madonsela reportedly said that in the final stages of the investigation, Zuma's team suggested a date which fell after the end of her term in October that year.
Madonsela told Business Day that Zuma was not being honest.
She reportedly said that he knew that he had been invited to an interview. He was reportedly also sent a Section 7(9) notice [which informed him that he had been implicated in the state-capture investigation].
"He and two of the Gupta brothers took off to Dubai and claimed they'd be there for three weeks.
"We asked if they could be interviewed via Skype or we could send a team and they said they could not co-ordinate with their lawyers," Madonsela told Business Day.
The inquiry is expected to continue at 10:00 on Tuesday.
Watch the proceedings live on News24.