As reported by The Sun, Cowell suggests in new unauthorised biography The Intimate Life Of Simon Cowell that if he were gay, he would have no reason to hide the fact.
He said: "If I was gay, why wouldn't I admit it? It wouldn't harm me and my mother wouldn't freak out."
Cowell is also quoted as saying anyone who doubts that he is telling the truth is "mad".
Journalist and author Tom Bower, who interviewed numerous friends, acquaintances and business associates of Cowell for the book, said that he had found no evidence to support the idea that Cowell is gay.
He wrote: "The pertinent fact is that not a single man has offered any evidence of an advance by Cowell despite the promise of enormous financial reward."
Several revelations about Cowell have come out of extracts already published from the book, including his relationship with Dannii Minogue and the fact that he has two Botox sessions a year.
Cowell's long-time publicist Max Clifford has said he is "disappointed" that Cowell chose to co-operate with Bower on the book.
It was revealed this week that Cowell had his computer and wallet stolen by a woman with whom he had a one-night stand.
Watch Digital Spy's recent interview with Cowell below: