Serota asks artlovers to solve mystery of 600 works that may have been looted by the Nazis

Up to 600 artworks in British museums and art galleries may have been looted by the Nazis during the Second World War, according to the National Museum Directors' Conference.

Up to 600 artworks in British museums and art galleries may have been looted by the Nazis during the Second World War, according to the National Museum Directors' Conference.

Despite a painstaking trawl through the nation's art archives, experts have so far failed to prove whether or not the artworks were looted during the 1939-1945 war and they are now calling for help from the public.

There are about 600 items whose whereabouts during the war are unclear, and researchers said they were "desperate" for help in tracking the hidden history of the works.

In February, 10 institutions, including the British Museum, published lists of works in their collections whose histories could not be accounted for between 1933 and 1945.

The list originally contained 350 items but has now grown to 600 as researchers have recently found more works with unclear backgrounds.

Sir Nicholas Serota, chairman of the working party set up to investigate the issue of art that may have been stolen during the Holocaust, said: "We are encouraging people to come forward with information. We depend on people coming to us with information to help us fill the gaps.

He added: "People could have the smallest pieces of information that could be crucial for us in determining where a piece of art was in the period 1933 to 1945."

The lists include works by Degas, Courbet and Caravaggio as well as sculptures, drawings and miniatures. Examples include a valuable 15th-century miniature crucifix purchased at an antique shop in Cirencester in 1943 by a Mr Wyndham Payne from Sidmouth, Devon.

Mr Payne died in 1974 and the British Library, which now holds the miniature, cannot say for certain that it was not looted during the war.

Dr Alice Prochaska, director of special collections at the library, said: "We have no reason to believe that since the 15th century it ever left the British Isles ... and we don't know how it came to be in that antique shop. We don't even know which antique shop it was."

Yesterday the NMDC published an updated report of works of art with which it needs assistance; details of the works are available on its website, www.nationalmuseums.org.uk. It also reported for the first time on the plans drawn up by 14 regional museums to scour their own collections.

To date the national museums and galleries have only received one claim in connection with works in their collections, which related to a painting of Hampton Court Palace by Jan Griffier at the Tate. The claim is now being assessed.

Dr Alan Borg, chairman of the NMDC, said: "It's still early days for the national museums as well as the regional ones. Those who may turn out to have a claim may not know about it at the moment. They could be in a state of mind where they don't want to think about what happened during the war and to their families."

The museum with the most challenging research task is the British Library, which currently has holdings of more than 80 million items and its investigations are expected to last for many more months.