That Germany must make greater efforts to locate, identify and return art looted during the Third Reich is well known in the art world.
But Der Spiegel magazine reported over the weekend that a carpet of unclear provenance that came from Hermann Göring's collection was in Angela Merkel's Chancellery. Tapestries from the same collection were hung on the walls of the government's guest house in Bonn, the magazine reported.
Peter Gauweiler, a veteran MP from the Bavarian Christian Social Union, sister party to Merkel's Christian Democratic Union, called on Tuesday for new ideas of how to cope with the huge number of art works concerned. Der Spiegel suggested that only 84 museums had completed a full provenance check - out of 6,300 museums in the country.
Gauweiler, who is head of the parliamentary committee for foreign cultural and education policy, said the topic needed to be discussed. "How we deal with these works of art also influences the reputation of the federal republic abroad," he told the magazine.
"We have to deal with this freed from the shadows of the past," he added.
Former secretary of state for culture Michael Naumann told Der Spiegel at the weekend the legal framework for returning art that had been stolen or bought cheaply when the owners were under duress - or paying compensation - to heirs.
He said more money was needed for research into provenance of artworks, and suggested that €10 million be taken for this from the budget already earmarked for a new museum for the Sudeten Germans who were driven out of the Czech Republic after the war.
The Nazis had collected nearly five million pieces of art by the end of the war - stolen from across the continent and hidden in 1,500 depots in various countries. Many were destroyed after 1945, many also stolen by soldiers or civilians, but by 1950 it is thought around half had been returned to their original owners, Der Spiegel said.
But many thousands are still in museums, while around 20,000, including 2,300 paintings are in the possession of the government, the magazine said.
Museums should really check all their exhibits acquired since 1933 to make sure they have good records of legitimate sales, but this would require an enormous and expensive effort. The Bavarian state painting collection has one employed art historian who is supposed to check the provenance of 4,400 paintings and 770 sculptures, which as Der Spiegel said, would be a life's work.
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Art restitution cases still reach court on a regular basis, when heirs to mostly Jewish but also other Nazi victims manage to track down works of art and make a claim. But many say it should be the responsibility of those museums in possession of the art to contact the heirs.