updated 07/15/2014 AT 3:00 PM ET
•originally published 07/15/2014 AT 9:00 PM ET
To Kill a Mockingbird author Harper Lee has again spoken out against a memoir that she claims is unauthorized.
Former Chicago Tribune reporter Marja Mills wrote The Mockingbird Next Door: Life with Harper Lee, which hits bookstores Tuesday, and documents the 18 months that Mills spent living next door to Lee and her older sister, Alice, in Alabama. The book was published with their blessing, according to Penguin Press.
However, Lee insists that once she realized Mills intended to write “another book about Harper Lee,” she “cut off all contact with Miss Mills, leaving town whenever she headed this way,” she says in a statement published by Entertainment Weekly. “Rest assured,” Lee writes, “as long as I am alive any book purporting to be with my cooperation is a falsehood.”
Mills, however, sticks by her memoir. “I can only speak to the truth, that Nelle Harper Lee and Alice F. Lee were aware I was writing this book and my friendship with both of them continued during and after my time in Monroeville,” she tells PEOPLE in a statement.
“In addition, Nelle’s good friend, Tom Butts, who I had the pleasure of getting to know during the course of writing this book and who remains a friend to this day, is also on the record in support of my work,” Mills says. “I am so grateful for my time with the Lee sisters. It was the honor of my life when they both gave me their blessing to write my book.”
This is not the first time Lee has documented her displeasure with Mills’ book. When Penguin Press first announced the acquisition of the memoir in 2011, Lee released a statement denouncing the book through the law firm, Barnett, Bugg, Lee & Carter in Monroeville, Alabama.
“Contrary to recent news reports, I have not willingly participated in any book written or to be written by Marja Mills,” she wrote. “Neither have I authorized such a book. Any claims otherwise are false.”
However her sister Alice Lee, who practiced law until she was 100 years old, claimed at the time that Nelle may not have understood the 2011 statement when she signed it, since she had suffered a stroke in 2007.
“Poor Nelle Harper can’t see and can’t hear and will sign anything put before her by anyone in whom she has confidence. Now she has no memory of the incident, ” Alice Lee wrote.
Check out PEOPLE’s review of The Mockingbird Next Door in this week’s issue, on newsstands Friday.