In a new revelation, it has come to light how the German publishing house Springer handed over the only known original blueprints of the Auschwitz concentration camp to Israel despite promising to give them to the German government, which considers the considers the blueprints its property.

Details of the controversial 2009 transfer were inadvertently revealed by "Bild" editor-in-chief Kai Diekmann.

In an interview with the Israeli online magazine "Spitz" this week, Diekmann said that he had handed over the blueprints - complete with Heinrich Himmer's signature - to Israeli Prime Minister Benjamin Netanyahu during a visit to Berlin.

At the time the blueprints were on display the Springer publishing house - one of Europe's largest digital publishers that owns Bild - after having been bought on the black market for an undisclosed sum.

Springer had the blueprints checked for authenticity with the German Federal Archives, which found them to be authentic. Springer also allegedly promised to give the blueprints to the Archives, which alongside the Interior Ministry considers the original document to be state property.

The Interior Ministry even told Springer that it would be stopped at the border if the anyone tried to bring the documents out of the country.

That is, anybody except Netanyahu, apparently. Diekmann had it in mind to give the blueprints to Israel to keep at the Yad Vashem Holocaust Memorial. He therefore arranged a meeting with Netanyahu in Berlin during one of his state visits and gave it to the Israeli leader.

The transfer to Israel was a "great disappointment," according to Hans-Dieter Kreikamp, who at the time was the manager of the "German Reich" section of the Federal Archives in Berlin.

Germany still owns a copy of the blueprint, but that is still not as good as the original.

"The difference between a good copy and the original is the sense of authenticity. A serious researcher would naturally like to examine the details. And one can only do that with the original," he said.