A federal jury in the United States has indicted the former chairmen of the world's two largest auction houses, Sotheby's Holdings and Christies International, on charges of conspiring to fix the commissions paid to auction houses.

The US Justice Department said the charges - against Alfred Taubman and Anthony Tennant, respectively former chairmen at Sotheby's and Christies - related to commission rates charged to sellers in the US and elsewhere between 1993 and 1999.

It said sellers in the US alone were charged more than $400m in commissions during the six years of the alleged conspiracy.

Christies and Sotheby's are reported to control more than 90% of the world's live auctions of art, jewellery and furniture.