News suggesting the singer enjoyed some steamy bedroom sessions with Simon emerged earlier this year when unofficial biography Sweet Revenge: The Intimate Life of Simon Cowell, by Tom Bower, was published in April.
The pair was said to have grown close when they both worked as judges on The X Factor between 2007 and 2010 and, until now, Dannii had kept quiet on the matter.
The star now insists she hasn't read the gossip about her personal life but wishes the author of the book and Simon well.
She told Glamour magazine: "I haven't read the book, but I've been told about the excerpts that relate to me, and the speculation about my private life. From what's been reported they put hundreds of hours into making this book, and Tom is a respected journalist. I'm sure it makes for a great read and I wish them all the best."
Dannii also spilled the beans on her reasons for not returning to The X Factor this year following Kelly Rowland's departure from the judging panel and it had nothing to do with any bad blood between her and Simon.
She said: "I was offered the chance to return, but I decided it wasn't right for me, as yet again it didn't fit in with the commitments I'd already made to Australia's Got Talent. I am fiercely passionate about every show I commit to. I had four incredible years on The X Factor, but the show has moved on, and so have I.
"The public went on a journey with me on The X Factor. When times were tough, you could see it there on the screen. It will always have a special place in my heart. I don't want people to think I just left the show and cut myself off from it, because I haven't."
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