Newman's secret sex life the subject of scandalous new expose
Porter interviewed Brando about Newman before the acting great died in 2004 - and he was stunned with what the heavyweight star let slip.
In his book, Paul Newman: The Man Behind The Baby Blues, he quotes Brando as saying, "He never fooled me. Paul Newman had just as many on-location affairs as the rest of us, and he was just as bisexual as I was. But, where I was always getting caught with my pants down, he managed to do it in the dark."
Porter tells America's the Globe he has been tracking Newman's secret sexual encounters since he met the actor in 1959 and alleges in his new book the late star, who was happily married to actress Joanne Woodward for 50 years, bedded icons like Grace Kelly, Judy Garland, Natalie Wood and Marilyn Monroe.
The writer also claims Newman and James Dean had a gay romance.
But the actor's family has dismissed Porter's book, claiming the sex allegations are "disgusting".
A source says, "Paul knew there were rumours out there about his sexuality and to have to face them when he's not here to dispute them is Joanne's worst nightmare."