The Dutch publisher of the controversial book that claimed to identify Anne Frank’s betrayer has apologised.

Ambo Athos has also suspended further prints of The Betrayal of Anne Frank: A Cold Case Investigation after worldwide backlash for suggesting a Jewish man named Arnold van den Bergh was responsible for revealing Anne Frank and her family’s hiding place to the Nazis during World War II.

Anne and seven other Jewish people were found by the Germans in a secret annex above a canal-side warehouse in Amsterdam in August 1944. They were taken away to concentration camps, with only the teenager’s father surviving the war.

In an internal email to the Canadian author Rosemary Sullivan and fellow researchers, the Dutch publisher said it should have taken a more “critical stance” before releasing the book to the world.

Ambo Athos said its new outlook had “gained momentum” following the book’s international publication.

The book’s investigation team, which included historians, filmmakers and former FBI agents, spent six years cracking the cold case, using modern investigative techniques and computer algorithms to search for connections to the teenager’s betrayal.

However, the results were met with widespread criticism after their release in mid-January, with some authorities describing it as “defamatory nonsense”.

The Anne Frank Fund was extremely critical of the research it was revealed.

“This does not contribute to truth-finding, it only creates confusion,” chairman John Goldsmith told Swiss media.

“The investigation is also full of errors.”

The Anne Frank House museum, which occupies the Amsterdam building in which the family hid, was also dubious. It said it was “impressed” by the investigation, but that questions remained unanswered.

“I don’t think we can say that a mystery has been solved now. I think it’s an interesting theory that the team came up with,” museum director Ronald Leopold said.

According to Dutch public broadcaster NOS, the principal investigator of the Anne Frank team, Pieter van Twisk was “perplexed” by the email from Ambo Anthos.

He said the team never claimed to have uncovered the definitive truth, publishing a “probability percentage of at least 85 per cent”.

Filmmaker Thijs Bayens, whose idea the investigation was, also said “we don’t have 100 per cent certainty”.

“We have investigated over 30 suspects in 20 different scenarios, leaving one scenario we like to refer to as the most likely scenario,” he told The Association Press when the research was revealed.

“There is no smoking gun because betrayal is circumstantial.”

Anne Frank’s diary, which was published after her death, is the most famous first-hand account of Jewish life during the war. It is renowned as a symbol of hope and a poignant glimpse into the Holocaust.