South African heavyweight Francois Botha has decided to have another drug test to clear his name and wants the result of his fight against Sonny Bill Williams removed from his record.

In a statement released through his promoters on Monday, Botha said the test that Australian news media reported he had failed was administered by "a confidant” of Williams's manager, Khoder Nasser.

The veteran South African said the chaotic fight with the New Zealand rugby international was "a disgusting state of affairs" and "amounts to match-fixing." Williams won on points after coming close to being knocked out in the final round.

Botha has asked his manager to apply to have the result removed from his record, saying he was unaware the bout in Brisbane last Friday had been shortened from twelve to ten rounds.

Australian newspapers reported Botha had tested positive for the banned stimulant phentermine.

He said the person who administered the drug test was "either a relative or a friend" of Nasser. "I had a drug test a few days before the fight but when I asked for the results I found out it was not official."

The fight was originally advertised as a twelve-rounder as required by WBA rules for title bouts.

"I had Williams in all sorts of trouble in the tenth round. There was no way he was going to last one more round, let alone two; he was out on his feet," Botha said.

Regional WBA representative Brad Vocale said he had doubts as to whether the fight was ever sanctioned by the organisation and that "sadly, boxing has been given a black eye again."

The chaos at the tournament came days after the Australian Crime Commission released a report identifying significant use of illegal substances in professional sport in the country, along with possible match-fixing and manipulation of betting markets.

The fight was initially scheduled as a ten-rounder for November last year, according to Botha's promoter, Tinus Strydom, but was postponed after Williams was injured while playing rugby.

It now seems Williams' management applied for the bout to be upgraded to a WBA International title fight, allegedly without Strydom's knowledge.

"When I first heard about it I did not think the WBA would grant it. Therefore I did not question the development because I firmly believed the fight's status would not change," Strydom said.

"However, Khoder's promotion material, both television and print in Australia, advertised the bout as a twelve-rounder."

When he arrived in Australia a week before the tournament, Strydom said, it "seemed a foregone conclusion" that it had been declared a 12-rounder and that Williams's manager had succeeded in acquiring WBA International title status for the bout. It has been reported that no WBA officials attended the tournament.

"Just before the start of the bout, the Aussie officials who were overseeing the tournament called me and pointed out that my contract was for a ten-round bout, and that's the way it was going to be," Strydom said.

"It was correct since the contract details were never altered after the November postponement. I immediately informed Botha's trainer, Hardy Mileham."

Strydom said Mileham, who was left fuming in a television interview after the fight, had asked referee Tony Kettlewell, who confirmed that it would be fought over twelve rounds.

"I have not heard from Australia's boxing officials or from the WBA, but my gut feel is that the bout will be declared a no-contest because of the conflict created by the advertisements, which declared that the bout was a twelve-rounder," Strydom said.

Botha said Kettlewell had confirmed before the fight that it would be held over twelve rounds.

"From the start of the bout, my strategy was to pace myself over twelve rounds, and from round seven I started turning on the pressure," he said. "After nine rounds I was quite happy with my progress and then all of a sudden I hear the ref say 'final round, shake hands'.”