The writer's latest revelations about Cowell are based on his relationship with ITV, who he has worked with on talent shows for over a decade. Bower has alleged that Cowell is annoyed at ITV for not being more supportive following the news about his private life.
"ITV are shooting themselves in the foot by criticising Cowell," said Bower.
"They are risking a self-destructive war by not respecting the man who has saved their channel from bad ratings when they have failed to create other original and attractive programmes. Without Cowell their ratings would sink.
"At the same time he is suffering because of the poor programmes that screen before his shows that they're responsible for. Cowell's view is that he is doing an amazing amount for them. He is relentless and knows the business better than anyone else.
"He is a perfectionist and they are certainly ungrateful."
Earlier this week, it was claimed that Cowell was annoyed at ITV's decision to rehire Gary Barlow as a judge on The X Factor for a second year, while ITV director Peter Fincham apparently prefers not to have Cowell involved directly in the talent shows.