The So MACho singer, who dated Cowell in the 1980s, is one of the music mogul's closest confidantes and often holidays with the star alongside a series of his other former flames, including Jackie St Clair, Terri Seymour and ex-fiancee Mezhgan Hussainy.
Following years of gossip suggesting Cowell maintains sexual relationships with all the women, Sinitta has now spoken out to put the rumours to bed.
She tells Britain's The Sun, "We never were a harem. We're not all sleeping with him. It's as bad as calling us his b**ches. It's rude, degrading and beyond insulting to suggest that. We're all grown ups.
"If people don't stop calling us his harem I will go nuts. The girls are all there with partners or as friends."
The singer also denied reports she is bankrolled by The X Factor boss: "I have worked for the money he has paid me legitimately. Yes, he takes us all with him in his plane, on his boat and in his villas. It is extremely generous, but this is not why I am his friend.
"I don't live for the holidays. It's the company and quality time together."
Sinitta has set the record straight about her relationship with Cowell in a series of interviews in the U.K. publication after revealing she underwent an abortion when she fell pregnant with his child in the '80s. The British star also admitted she was desperate to marry Cowell for years after the romance ended.