SOTHEBY’S and Christie’s have agreed to pay $40 million (£25 million) between them to settle an antitrust class action involving clients who bought and sold artwork through the firms’ non-US offices.

The settlement covers about 150,000 people, mainly in the UK and Canada. The case, subject to court approval in New York, covers auctions outside America between 1993 and 2000.

Advertisements will be placed to encourage potential claimants to come forward. The bulk of the settlement has been set aside for sellers.

The settlement is the last in a series of class actions arising from the price-fixing scandal in which Sotheby’s and Christie’s conspired to fix commissions. In 2000 the two auction houses agreed to pay $256 million each to compensate clients for illegally co-ordinating the commissions they charged on sales. Sotheby’s was also fined $45 million by the US Department of Justice and $20 million by the European Commission. Christie’s won exemption from the fines because it was the first to come clean on the price-fixing.

Commission lawyers said Christie’s had received “full leniency” because of a 1996 ruling offering full or partial immunity from fines for companies providing decisive information on price-fixing or market sharing. The fine imposed on Sotheby’s by the Commission was reduced by 40 per cent in acknowledgement of its partial co-operation.

Alfred Taubman, chairman of Sotheby’s, is serving a ten-month prison sentence for his role in the affair. His former Christie’s counterpart, Sir Anthony Tennant, faces arrest if he visits America.

Both firms hope the settlement will allow them to draw a line under a shameful period in their history.

Stephen Alexander of Class Law, which represented about 70 UK claimants, said the action was the “last piece in the jigsaw” of claims against the two auction houses. The size of individual settlements depended on how many people come forward.

Sotheby’s recently raised $175 million through the sale-and-leaseback of its New York headquarters. It has scaled back its internet activities, including closing its sothebys.com website, and claims to have cut costs by more than $70 million in the past three years. Last month Sotheby’s abandoned attempts to find a buyer for the controlling 62 per cent voting stake held by the Taubman family.

The scandal erupted in early 2000 when Christie’s cut a deal with US Department of Justice officials investigating allegations of price-fixing.

Herbert Black, a Canadian scrap-metal millionaire and art collector, duly filed a civil suit against the firms.