The head of the World Jewish Congress is calling on the German government to up efforts to return Nazi-looted art to its rightful owners.

Ronald Lauder made the comments Wednesday after a prosecutor in Augsburg announced he wants to return pieces from the now infamous Munich art trove to the hoarder the pieces were initially seized from.

“The conduct of the Augsburg prosecutor has been less than exemplary. After keeping the find secret for nearly two years it now appears that he wants to rid himself of a problem that he has been unable to handle properly for a long time,” Lauder said.

“That is irresponsible. This issue should be dealt with at the highest political level and not be left with a single prosecutor in Augsburg.”

Cornelius Gurlitt was discovered to be sitting on a collection valued at more than $1 billion, consisting of Nazi-looted works taken primarily from Jewish victims of World War II. The collection contains pieces from some of the 20th century’s most famed artists—Matisse, Chagall, Klimt, and more.

Now, Lauder wants German authorities to address more acutely the problem of Nazi-looted art, to ensure descendants of original owners receive their rightful property.

“A great deal of Nazi-looted art remains to be discovered. Some German museums have attempted to locate looted art in their collections but most are not devoting the resources needed to do this work or giving provenance research the priority it deserves,” Lauder added.

“The principal obstacle to the recovery of Nazi-looted art that is in private hands is the statute of limitations because it prevents judicial inquiry and recovery. The problem should be addressed by the German government because the Holocaust is unique and the statute of limitations was never intended to deal with massive wartime looting perpetrated in the course of genocide.”

Gurlitt inherited the trove from his father Hildebrand Gurlitt, and maintains his father was an art hero who worked to save priceless pieces from Nazi hands. But government officials assert Hildebrand was well aware of where the art was coming from as he actively acquired the pieces.

The return of Nazi-looted art has become a growing enterprise in Europe, with institutions like Versailles coming under inquiry over the origin of some of its most acclaimed works.