TV
It is thought that Catherine Tate led the voting for the People's Choice award but the prize was given to Ant and Dec instead to ensure Williams's attendance.
Law firm Olswang made the discovery after it was hired by ITV to investigate the awards show.
Olswang's report read: "Robbie Williams was invited to present an award. It was understood that he would be happy [to do so] if the recipients were Anthony McPartlin and Declan Donnelly.
"In order to ensure his attendance, this assurance was given."
However, the report added that it couldn't verify if Williams's agreement led to the wrong winner being announced.
"There is no suggestion that Robbie Williams, Anthony McPartlin or Declan Donnelly were aware of any of these issues."
Ant and Dec have agreed to return their prize.
ITV was today fined £5.86 million by regulator Ofcom for abusing premium rate phone lines.
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