The Pistorius family has denied in the "strongest terms" the athlete took acting classes in preparation for his murder trial, following accusations that he was "coached" by a professional actor.
In an open letter, British-born columnist Jani Allan accused him of faking his courtroom tantrums and described the athlete, who is accused of murdering girlfriend Reeva Steenkamp on Valentine's Day last year, as a "faux hero".
"I have it from a reliable source that you are taking acting lessons for your days in court," Ms Allan wrote. "Your coach has an impossible task."
She continued: "Oscar, I look at you mewling and puking in the witness stand. You truly represent everything the West loathes about white South Africans who live extravagant lives."
Anneliese Burgess, a spokesperson for the Pistorius family, dismissed Ms Allan's letter as a "mockery of the enormous human tragedy involving the Steenkamp family and our client and his family".
She added: "We deny in the strongest terms the contents of her letter in as far it relates to our client and further deny that our client has undergone any acting lessons or any form of emotional coaching."
Ms Burgess said Ms Allan, who claims to have sources close to the athlete, has never met Pistorius and described any knowledge she professes to have of him as "fictitious".
Pistorius' court appearances have been marked by dramatic shows of emotion, often breaking down in loud sobs and even vomiting at the sight of graphic evidence.
In cross-examination, state prosecutor Gerrie Nel accused a seemingly grief-stricken Pistorius of shedding tears of self-pity to avoid answering difficult questions about night he shot and killed his girlfriend through a locked toilet door.
Pistorius's loud sobbing and wailing have prompted Judge Thokozile Masipa to temporarily adjourn court in multiple occasions so he could "compose himself" before continuing giving evidence.
Pistorius is accused of murdering Ms Steenkamp following a domestic dispute in the early hours of Valentine's Day last year. He claims he shot and killed his girlfriend in a case of mistaken identity, thinking she was an intruder.
The trial has now adjourned for a break and will reconvene on Monday 5 May.