"The thing that bothers me about this whole thing is that Khoder Nasser's brother or family member was the person who admitted the drug test," Botha said.
Nasser laughed off that accusation on Campbell Live and said Botha was doing a great job of drumming up interest in a potential rematch.
"The pathology company is a very reputable pathology company in Australia.
"If he wants to validate himself, why doesn't he go get a reputable South African urine examination and come out with those papers? Why didn't he do that immediately?"
Botha said he would take Nasser up on his offer as soon as possible.
"I will have a drug test in South Africa and I will ask for the results in 24 hours, and then I will make it known to the world."
Meanwhile, Williams' next fight may not feature the "pick the round" betting option, the TAB has said.
Williams' unanimous points victory prompted a storm of controversy surrounding the length of the bout, with 12 rounds cut to 10.
The TAB was forced to refund all "pick the round" bets and yesterday announced it would hold the right to remove the option in future.
