A former sports agent of O.J. Simpson has revealed that the sports star confessed to killing his ex-wife Nicole Brown Simpson.

In his new book How I Helped O.J. Get Way With Murder, Mike Gilbert claims that he aided Simpson during his murder trial, and advised him to take arthritis medicine to bloat his hands so they wouldn’t fit the murder glove.

Gilbert also claims Simpson then confessed to the killing while high on marijuana, after he was acquitted.

His book quotes the ex-American footballer revealing Brown Simpson was killed with a knife she opened the door to him carrying: "If she hadn't opened that door with a knife in her hand ... she'd still be alive."

Gilbert writes, "Nothing more needed to be said. O.J. had confessed to me. There's no doubt in my mind."

Simpson has since dismissed the book's claims. His lawyer Yale Galanter described the author as "a delusional drug addict who needs money. He's fallen on very hard times. He is in trouble with the IRS."

He adds: "I've talked to O.J. about it. This stuff not only didn't occur but it's not factually supported by the evidence."