Under international norms adopted in Washington in 1998, German museums are obligated to go through their collections for works that may have been looted by the Nazis. But the museums have balked at going a step further and digitizing their collections to allow independent searches, citing budget restrictions and a lack of staff.
That reluctance has for years been a source of tension within the art world, with critics alleging other motives. "They don't want to let people see what they have because they know if they put it online they'll get claims and possibly lose major paintings," Ronald Lauder, a billionaire art collector and president of the World Jewish Congress, said in an interview.
The Munich discovery has prompted his group as well as the U.S. government and the London-based Commission for Looted Art in Europe to press for change.Germany is coming under growing international pressure in the wake of the Munich art discovery to force its museums to disclose the full inventory of works they hold. German museums are balking, citing understaffing and underfunding.
Stuart Eizenstat, U.S. Secretary of State John Kerry's special adviser on Holocaust issues, said he doesn't understand how Europe's largest economy cannot afford the relatively inexpensive process of putting its public collections—particularly works created before 1945—in an online database similar to those set up years ago in the U.S. and the U.K.
"Germany has done so well economically that it needs to set an example on this," said Mr. Eizenstat in an interview.
The Munich art trove was found in the apartment of Cornelius Gurlitt whose father Hildebrand was a major art dealer for the Nazis. Cornelius Gurlitt, 80 years old, hasn't been charged with any wrongdoing.Among the works found was a Matisse that has long been registered as missing on Lostart.de, the German government's official database for art looted during World War II.
Critics of Germany's handling of the Gurlitt case say authorities should have immediately disclosed the discovery of any works registered as stolen. Local officials involved in the investigation, initially over suspected tax evasion, have said privacy laws prevented any disclosure.
German museums also cite privacy as a reason for not putting their entire collections online. Mr. Eizenstat challenged that, however, saying, "It is mystifying whose privacy they're trying to protect."
Germany has invested in provenance research, for instance by setting up the Magdeburg-based Lost Art database, but the onus remains on museums to carry out the legwork. Few have set up broad digital resources internally, and no centralized list exists.
The 15 collections of national museums based in Berlin are "far from all digitized," says Jörn Grabowski, head of its central archives.
Many art experts consider the holdings of Bavarian museums to be the richest. The 25,000 works as well as their supporting documents of provenance are all digitized for museum employees to access internally, says Martin Schawe, managing director of the Bavarian State Picture Collection.
Mr. Schawe said putting those documents online for the public would be too expensive, although he said he has never looked into exactly how much it would cost. He added that appealing for private funding wouldn't work.
No one would give us money for that. They would say it was the government's job," he said.
Mr. Lauder called the cost argument baseless. "The issue is attitude and hostility, not lack of technology," he said.
Officials at the German Culture Ministry didn't respond to requests for comment.
Germany allocates €3 million ($4 million) annually to its federal provenance investigation center. Art galleries can apply to the center for funding to hire their own researchers.
Ulrike Lorenz, director of the Kunsthalle Mannheim in southwestern Germany, said her institute has done that for the past two years.
The Kunsthalle Mannheim lost some 800 works during the Nazi "degenerate art" purge of 1937, and one of them showed up in the Gurlitt collection—a drawing by Ernst Ludwig Kirchner—which the museum hopes to recover.
Ms. Lorenz said it plans to place its roughly 34,000 works on paper online by 2015, but said it would probably be at least five years before the institute gets its entire collection, including 1,900 paintings online.
"In Germany, there hasn't been the transparency that there is long been in the Anglo-Saxon world," said Ms. Lorenz, attributing it to fears of being overwhelmed by loan requests.
While Germany is under fire over the Gurlitt case, art historians say it has been more progressive than Russia in dealing with the legacy of looted art. Soviet troops seized vast amounts of art from European museums and collectors toward the end of World War II and, in some cases, kept it secret until the early 1990s.
The issue resurfaced in June when German Chancellor Angela Merkel nearly canceled an appearance with Vladimir Putin amid a dispute over artwork on display at the Hermitage in St. Petersburg that had been looted from Germany.