Khodder Nasser has labelled Francois Botha "a sore loser" after the South African claimed he was offered $150,000 to throw his fight against Sonny Bill Williams.
Botha alleges Nasser, Williams's manager, had offered him the sum in a Brisbane park on Tuesday last week, three days before the supposed World Boxing Association (WBA) title fight which Williams won on points.
Botha's remarkable claim is the latest twist in a scandal that has also included a positive drug test and claims the fight was ended two rounds too early.
Nasser says the 44-year-old Botha needs to come to terms with the fact he "got his ass whipped" by Williams.
"I think he (Botha) is still in a daze," Nasser said.
"This is the same bloke who said he didn't know about the fight being 10 rounds, and then his promoter and he himself came out later and said it was 10 rounds.
"Then he said he wasn't drugs tested and then he said he was tested, then he said he was tested by my brother, and now he has come up with this one (bribe allegations). What is next?
"The fact the media is loving this sore loser must be unprecedented, the media is siding with a guy who has got sour grapes.
"He has got to come to terms with the reality that he got his ass whipped by a guy (Sonny Bill Williams) who had had only five fights.
"It is all well and good to come out with all these allegations after, but where's his manhood? Why wasn't it bought out the day before? It's absolute madness.
"If it happened like he said, why didn't he come out and report it then - or does it suit him now?"
Botha made the allegation against Nasser on a New Zealand radio station on Wednesday morning.
Speaking from Durban, Botha said he received a phone call from Nasser asking him to be picked up but to be alone.
"I wasn't told where I was going. As we stopped at a park, my cellphone was confiscated and was given to a guy in the car," Botha said.
"Then I was being walked (by Nasser), and during this walk, I was offered $150,000 to throw the fight.
"I just said `no, I can't do it'."
Botha confided in a close friend when he returned to his hotel and they decided then to take the matter no further.
"He could clearly see I was very upset. He told me `Francois, if you are even thinking about doing this, I'm going to get on the plane and go back to South Africa'."
The fight has been mired in controversy, most notably over the length of the fight, which was completed after 10 rounds.
Both sides have disputed what they understood the length of the fight should be, with Botha still adamant he had prepared for a 12-round affair.
He finished strongly and says another two rounds would have been enough to secure victory over tiring former All Black Williams.
The South African is also dismayed by reports he had failed a pre-fight drug test, which reportedly revealed the presence of a banned stimulant.
Nasser said the testing process was credible, which Botha disputes.
He said he had been drug tested upon return to South Africa and the results were "all clear".
Doubts have also been raised about whether the WBA actually sanctioned the bout, and if Williams' claim on the title is legitimate.
There was no WBA official present in Brisbane for the fight.