The Queensland branch of the Australian National Boxing Federation says a contract signed by Francois Botha and Sonny Bill Williams stipulated their fight on Friday would only go 10 rounds.
The Brisbane bout, which had been advertised as lasting 12 rounds, was stopped after 10 and awarded to Williams on points.
Botha says he was expecting a 12-round bout and has threatened to appeal the decision.
Queensland secretary Jim Youn, says Botha's and Williams's managers met the judges and timekeeper before the fight to confirm it would only go 10.
Meanwhile, the TAB says it will continue to take bets on bouts featuring Williams but reserves the right not to, if it doubts a fight's integrity.
TAB bookmaker Mark Stafford says that in future the agency will seek assurances a boxing match will go the advertised distance.
General manager Martin Saunders says Williams was involved in two previous fights where the number of rounds was reduced without notice and the agency is confused and disappointed by what happened on Friday, as it had been told the bout was scheduled for 12 rounds.