A Jewish notary has been named by a cold case team led by a former FBI agent as the prime suspect for the betrayal of Anne Frank and her family to the Nazis.

Arnold van den Bergh, who died in 1950, has been accused on the basis of six years of research and an anonymous note received by Anne’s father, Otto Frank, after his return to Amsterdam at the end of the war.

The note claims Van den Bergh, a member of a Jewish council, an administrative body the Germans forced Jews to establish, had given away the Frank family’s hiding place along with other addresses used by those in hiding.

He had been motivated by fears for his life and that of his family, it is suggested in a CBS documentary and accompanying book, The Betrayal of Anne Frank, by Rosemary Sullivan, based on research gathered by the retired FBI detective Vince Pankoke and his team.

Pankoke learned that Van den Bergh had managed to have himself categorised as a non-Jew initially but was then redesignated as being Jewish after a business dispute.

It is suggested that Van den Bergh, who acted as notary in the forced sale of works of art to prominent Nazis such as Hermann Göring, used addresses of hiding places as a form of life insurance for his family. Neither he nor his daughter were deported to the Nazi camps.

Anne Frank hid for two years in a concealed annexe above a canalside warehouse in the Jordaan area of Amsterdam before being discovered on 4 August 1944, along with her father, mother, Edith, and sister, Margot.

The young diarist was sent to Westerbork transit camp, and on to Auschwitz concentration camp before finally ending up in Bergen-Belsen, where she died in February 1945 at the age of 15, possibly from typhus. Her published diary spans the period in hiding between 1942 and her last entry on 1 August 1944.

Despite a series of investigations, the mystery of who led the Nazis to the annex remains unsolved. Otto Frank, who died in 1980, was thought to have a strong suspicion of that person’s identity but he never divulged it in public.

Several years after the war, he had told the journalist Friso Endt that the family had been betrayed by someone in the Jewish community. The cold case team discovered that Miep Gies, one of those who helped get the family into the annexe, had also let slip during a lecture in America in 1994 that the person who betrayed them had died by 1960.

There were two police investigations, in 1947 and 1963, into the circumstances surrounding the betrayal of the Franks. The son of the detective, Arend van Helden, who led the second inquiry, provided a typewritten copy of the anonymous note to the cold case reviewers.

The author of the new book, Sullivan, said: “Vanden Bergh was a well-known notary, one of six Jewish notaries in Amsterdam at the time. A notary in the Netherlands is more like a very high-profile lawyer. As a notary, he was respected. He was working with a committee to help Jewish refugees, and before the war as they were fleeing Germany.

“The anonymous note did not identify Otto Frank. It said ‘your address was betrayed’. So, in fact, what had happened was Van den Bergh was able to get a number of addresses of Jews in hiding. And it was those addresses with no names attached and no guarantee that the Jews were still hiding at those addresses. That’s what he gave over to save his skin, if you want, but to save himself and his family. Personally, I think he is a tragic figure.”