Simon Cowell's sex life has been documented in new book.

The music mogul has claimed in a new unauthorised biography, 'Sweet Revenge: The Intimate Life of Simon Cowell', that he had a secret affair with his former 'x factor' colleague Dannii Minogue in 2007 while the pair were judges on the talent show.

In the book, he says: ''I had a crush on her. It was Dannii's hair, the sexy clothes, and the t**s.

''I was like a schoolboy. She was foxy. She was a real man's girl. Very feminine. It was genuine love.''

Simon claims he started seeing Dannii - who earlier this month split from former rugby player Kris Smith after four years together - after he broke up from his long term girlfriend Terri Seymour in 2008, and he admits the Australian singer would ''get around'' him by playing the ''soulful victim''.

In quotes from the book published in The Sun newspaper, Simon said: ''She would come in dressed in her tracksuit and her slippers, drop her eyes and play the soulful victim to get around me. She played me. I adored her.''