The 52-year-old X Factor supremo split with the make-up artist, ending their wedding plans, after a series of rows.
Now journalist Tom Bower says in a new unauthorised biography that Cowell promised to transfer ownership of his £5m Beverly Hills house to Ms Hussainy, for being a “hopeless boyfriend”.
Cowell — who it was claimed at the weekend slept with former X Factor judge Dannii Minogue — had been engaged to Ms Hussainy since early 2010.
“I put her in the public eye and attracted a lot of attention to her. I had to be sensitive about her position and I didn’t want to hurt her family, with whom I had become very close,” Cowell is reported to have said about her.
Bower spent a year interviewing friends and colleagues of Cowell for his book, Sweet Revenge, as well as Cowell himself.
The media mogul reportedly described the engagement to Ms Hussainy — whom he has known since 2002 — as “a big mistake”.
Meanwhile, Minogue is said to be unhappy about the claims of an affair being chronicled in the book.
The 40-year-old singer recently split from her rugby player partner Kris Smith, with whom she has a 21-month-old son.
The publication of the book about Cowell on Apr 21 comes as his ITV1 show Britain’s Got Talent continues to struggle against BBC1 rival The Voice.
When the two shows clashed on Saturday night The Voice had twice as many viewers. The BBC1 show also had a bigger average audience than Cowell’s show for a second week running.