An exhibit at a Vienna museum displaying art alleged to have been looted by the Nazis has added fuel to the debate over the restitution of stolen art.

Clemens Jabloner, the president of the Administrative Court, one of the three highest courts of the Austrian judiciary, believes they should be returned to their rightful owners.

"On principle, everything of dubious origin should be returned," Jabloner told the Agence France Presse.

The alleged stolen artworks, which are on display at the Leopold Museum in Vienna, have prompted the opposition Green Party to call for the paintings to be restored to their previous owners. The party has dubbed the exhibition "the greatest display of looted art in Austria in years."

The head of Vienna's Jewish Community, Ariel Muzicant, called for the closure of the Leopold Museum last week until it complies with legislation on the restitution of looted Jewish property.

Austria passed the Art Restitution law in 1998 after a U.S. court seized two Egon Schiele paintings — apparently stolen from Jewish art collectors during the Second World War — from an exhibit in New York.

However, the law only applies to federal collections, and private museums aren't subject to the same legislation. The Leopold Museum is categorized as a private foundation, even though it was bought by the Austrian state in 1994.

The renowned museum, founded by Rudolf Leopold, owns some 5,000 artworks, including masterpieces by Klimt and the largest collection of Schiele paintings and sketches in the world.

Muzicant has asked that the law be modified to apply to private institutions.

The exhibition at Leopold Museum features over a dozen works of questionable origin, including those of Tyrolean painter Albin Egger-Lienz, an important Austrian artist in the 20th century.

One of the paintings was a 1910 painting of two peasants, stolen from Jewish architect Oskar Neumann and presented by the local Nazi leadership to Adolf Hitler on his birthday in 1939.

Austria's annexation by Germany on March 12, 1938, led to the systematic looting of Jewish property and assets, many of which were subsequently found in national public collections.

However, 82-year-old Leopold, who sees himself as "the greatest Austrian collector of the 20th century" has always denied knowingly acquiring stolen Jewish objects.

"Works bought legally and in good faith should be able to remain in Austria," he told the weekly magazine Falter, adding that heirs were "only interested in money."

Austria's law has enabled the restitution of thousands of artworks, including five major paintings by Gustav Klimt — four of which were auctioned off in New York in 2006 for more than $188 million Cdn.

With files from the Australian Broadcasting Corporation