An investigation described as “highly credible” has been published regarding the fate of one of the most notorious Nazi criminals to survive the war.

Alois Brunner was an SS officer who served as an assistant to Adolf Eichmann, one of the key architects of the Holocaust.

The Simon Wiesenthal Centre reported in 2014 that Brunner had died in 2010. However, the French magazine, XXI¸ which interviewed three former members of the Syrian Secret Service, published an article on Wednesday stating that Brunner had died in 2001.

Described by Eichmann as his “right hand man”, Brunner went on to command the Drancy internment camp in France, from which tens of thousands of Jews were sent to their deaths in the East.

For almost 50 years Brunner was granted asylum by the Syrian government, where he allegedly passed on Nazi torture methods to his hosts.

According to the ex-secret service sources interviewed by the magazine, Brunner was kept under virtual house arrest for the last decade of his life, with his final years spent in squalor in a single basement room.

Serge Klarsfeld, a Nazi-hunter, told AFP: “XXI's investigation is highly credible. They have questioned someone who knew him at close quarters.

“Until the end he kept his hatred of Jews intact, as well as his faith in National Socialism.”

A man alleged to have been Brunner told the Chicago Sun-Times in a 1987 phone interview regarding the Holocaust that “All of them deserved to die because they were the devil's agents and human garbage. I have no regrets and I would do it again."

The article also describes the last part of the Nazi’s life. According to one of XXI’s sources, Brunner “suffered and cried a lot in his final years, everyone heard him".

Mr Klarsfeld’s father was among those deported from Drancy to Auschwitz, where he perished.

Commenting on Brunner’s death, he said that he was “satisfied to learn that he [Brunner] lived badly rather than well”.