Vitali Klitschko's manager claims David Haye dodged a fight against the Ukrainian as he was too scared to take him on.
Haye came out of retirement this month when he announced a controversial grudge match against fellow Londoner Dereck Chisora that will take place at Upton Park on July 14.
The fight, which has had to be sanctioned by the Luxembourg Boxing Federation as neither fighter holds a British licence, has been widely condemned within the sport.
The German Boxing Federation today denounced the bout and the World Boxing Council have vowed to "expel" anyone from its organisation who is involved in the contest.
According to Bernd Boente, manager of both Klitschkos, Haye was offered the chance to fight WBC heavyweight champion Vitali in September but instead chose to take the "easier" option of taking on Chisora.
"There was a contract from us for (Haye) to fight Vitali in September but he chose to fight Chisora instead because it's an easier task," Boente told Press Association Sport.
"I think he never really wanted to fight Vitali. The guy is always talking. He barks like a dog and he does that because he is mostly afraid."
Haye has a long-running rivalry with the Klitschkos, who have dominated the heavyweight division for a large part of a decade.
The 31-year-old has goaded the Ukrainians by launching a phone application in which he beheads a fighter widely thought to be one of the brothers and he also once wore a t-shirt that depicted him holding aloft the severed heads of the famous heavyweight pair.
Haye's only fight against one of the brothers - last July's clash against Wladimir - ended with a significant points defeat for the Londoner - one he partly blamed on a broken toe.
The controversial former WBA champion has always claimed he is determined to unify the division by beating both brothers but that looks very unlikely now as Wladimir insists he will not fight him again and Vitali looks set to retire in October if he is elected to Ukraine's parliament.
"I don't think it (Haye-Vitali) will happen," Boente added.
"It will definitely not happen in September because we are already talking to a couple of different opponents for then and it is too close for Haye to fight him after his fight against Chisora.
"Wladimir will never fight him again. Why should he? There are no questions left for him to answer and Vitali... If he is elected in October he will quit his career, for sure."
The German Boxing Board has written to the European Boxing Union (EBU) and the British Boxing Board of Control (BBBoC) condemning the Upton Park fight, which was set up after Haye and Chisora brawled following the latter's defeat to Vitali in February.
The BBBoC has also strongly condemned the fight, but organisers insist the bout is legal and claimed last month that 20,000 tickets had already been sold.
Wladimir, speaking at the London premiere of the film Klitschko tonight, added his objection to the fight, saying: "It's a contest between two guys that have no licence and are fighting on British soil under a licence from Luxembourg. It's not even a fight.
"I think this is a story of a fight between two losers, two people who have lost to the Klitschkos."
Boente was stronger in his condemnation, adding: "It is a freak show.
"It's tough for this sport. It's only for the money. This is the entertainment business, yes, but it should not be allowed. "The only reason that this fight is happening is because they fought each other in a press conference in Munich. It's absolutely ridiculous.
"It sets a very, very bad example for kids. It more or less tells you - do the most horrible thing and you will get the most money for it. That is the message for the kids."
The film, which charts the lives of the brothers from their humble background in Ukraine to their current status as super stars, is a source of pride for Vitali.The 40-year-old said: "It's about the dream of two boys. They have a dream and they work a lot and hard and one day the dream comes true."