A report into the conduct of IAAF officials has a "wow factor", says Dick Pound - the man who helped compile it.
The World Anti-Doping Agency (Wada) commission investigation examined allegations of widespread doping in athletics and it led to Russia being provisionally banned from competition.
The second part of the report - held back because of a police investigation - focuses on claims against the IAAF.
"People will say how on earth could this happen," Pound said.
"When we release this information, there will be a wow factor," the commission chairman told the Independent.
"It is a betrayal of what people in charge of the sport should be doing."
The findings on athletics' governing body have not been released after a French police investigation began earlier this month into former IAAF president Lamine Diack and former head of anti-doping Gabriel Dolle.
Diack is being investigated over allegations he took bribes to cover up positive drugs tests. He has resigned from his position as honorary member of the International Olympic Committee, but has yet to respond to the claims.
Pound said the part of his report focusing on allegations against the IAAF looked likely to be released in January.
"One fear is that if we issue it on the Friday before Christmas, for example, no one will notice it and we want to have the maximum impact and deterrent," he said.