The Guardian newspaper reported Friday that according to the book—titled "The Backyard of the Secret Annex"—Dutch-Jewish collaborator Ans van Dijk reported their hiding place.
Van Dijk was executed after the Second World War for her collusion with the Nazis, after confessing to giving up 145 Jews, including her own brother and his family.
While it had been previously claimed she was also guilty of turning over the Frank family, the Anne Frank House museum in Amsterdam and its research center failed to reach any conclusion on the matter, despite studies and a police investigation into her actions.
In his new book, however, author Gerard Kremer, 70, claimed he has solved the mystery. Kremer's father was a member of the anti-Nazi Dutch underground, and was an acquaintance of van Dijk in Amsterdam.
The author's father, who died in 1978, was said to have been a caretaker in an office building in the Dutch capital, two floors of which were taken over by the German authorities and the Dutch Nazi organization—the NSB—during the Nazi occupation of The Netherlands.
Kremer's father recounted van Dijk's arrest by the Nazi intelligence service on the first day of Easter in 1943. After her arrest, she made frequent visits to the building, in costume, and used telephones in the appropriated offices.
The book further outlined that Kremer overheard talk in the Nazi offices in early August 1944 regarding the region where Frank and her family were hiding, and that van Dijk took part in those conversations.
Anne and her family members were arrested August 4, while van Dijk left Amsterdam for The Hague.
A spokeswoman for Anne Frank House told The Guardian that the museum contacted the book's author, but he could provide no evidence proving van Dijk's culpability.
"We consider Gerard Kremer's book as a tribute to his parents," she said, "based on what he remembers and has heard. In 2016, the Anne Frank House carried out research into the arrest of the Frank family and the other four people in hiding in the secret annex."
"Ans van Dijk," she continued, "was included as a potential traitor in this study. We have not been able to find evidence for this theory, nor for other betrayal theories."
After the war and van Dijk's move to The Hague, she was arrested at a friend's house on June 20, 1945. She was later charged with 23 counts of treason and brought before a special tribunal in Amsterdam, where she confessed to all counts and was sentenced to death.
Her subsequent attempts to appeal the verdict and receive a royal pardon, with the claim she was merely acting out of self preservation, failed and she was executed by firing squad in January, 1948. The night before her execution she was baptized and joined the Roman Catholic Church.