For some time, China has been trying to catalogue  the vast numbers of looted Chinese artefacts that have ended up in museums & private collections around the world. Based on data from UNESCO, it appears that of all the Museums holding disputed artefacts, the British Museum has by far the most with twenty three thousand in its collection (only two thousand of which are part of its permanent displays).
People’s Daily 
British Museum holds highest number of looted Chinese relics
15:57, October 25, 2010
Data from the United Nations Educational Scientific and Cultural Organization (UNESCO) shows that a total of more than 1.6 million Chinese cultural relics looted in the past are now housed in 47 museums worldwide, and the British Museum collected the largest number of them.
Currently, it has collected a total of 23,000 Chinese relics, and about 2,000 Chinese relics are on long-term display in the museum.
The British Museum’s collections of Chinese relics contains all types of art spanning across the entire history of China, including block-print editions, paintings and calligraphy as well as jade articles, bronze wares, pottery and ornaments.
Nine-tenths of the total 23,000 rare and ancient Chinese treasures are kept in 10 exhibition rooms in the museum. Ordinary tourists do not have the opportunity to see them unless they have special permission.