In the book "Love, Freddie" it is revealed that the child was the result of an affair the singer had with a close friend's wife, writes the British The Guardian.
Mercury is said to have met his daughter regularly and also gave her 17 volumes of his personal diaries.
The woman, who wants to keep her identity secret and is only referred to as B in the book, is today 48 years old and works in a care-related profession somewhere in Europe.
In a handwritten letter to biographer Lesley-Ann Jones, she writes: "Freddie Mercury was and is my father. We had a very close and loving relationship from the moment I was born and during the last 15 years of his life."
Her existence is said to have been known only to Mercury's inner circle. In another letter included in the book, B explains her reasons for sharing Mercury's diaries after 30 years.
"After more than three decades of lies, speculations, and distortions of the truth, it's time to let Freddie speak. That I choose to reveal myself now in middle age is solely my decision. I have not, at any point, felt forced to do this."
