Marja Mills' biography 'The Mockingbird Next Door: Life with Harper Lee', which released on Tuesday, claims to be a rare in-depth look at the lives of Lee and her sister Alice.
Mills, a former Chicago Tribune journalist, said she wrote the book after spending friendly time with the Lee sisters, whom she moved next door to in 2004.
But in a letter, the 88-year-old Lee, who never wrote another book after 'Mockingbird' and never grants interviews, said Mills' book had no cooperation from her, reported the Entertainment Weekly.
"Normally, I would not respond to questions about books written on my life. Miss Mills befriended my elderly sister, Alice. It did not take long to discover Marja's true mission: another book about Harper Lee. I was hurt, angry and saddened but not surprised," Lee wrote in her statement.
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Lee said she cut off all contact with Mills. She also slammed the author for saying that she has a written statement from Alice, who is now 100-year-old.
The 1960 novel, explores the racial inequality in the American south through the eyes of two children whose lawyer father is ostracised in his community for defending a black man, wrongly accused of raping a white woman.
The hugely popular book was adapted into an equally successful Hollywood film with Gregory Peck playing the role of morally upright lawyer. Peck won the best actor Oscar for his portrayal of Atticus Finch in the 1962 movie.