Tiffany sues Costco over engagement rings

Tiffany is suing wholesale club Costco for allegedly selling diamond engagement rings wrongly labelled as ‘Tiffany.’

The jeweller began an investigation last November after a customer claimed Costco had signs offering ‘Tiffany’ rings in a California store. Tiffany alleges this is a long-standing Costco practice.

"We now know that there are hundreds if not thousands of Costco members who think they bought a Tiffany engagement ring at Costco, which they didn’t," Jeffrey Mitchell, a lawyer for Tiffany, said in a statement.

The Tiffany case against Costco alleges trademark infringement, unfair competition, injury to business reputation, false advertising, counterfeiting and deceptive business practices. Costco is yet to respond publicly to the allegations.

Tiffany, as well as being a brand name, is also the term for a type of diamond setting commonly used for engagement rings. The Tiffany company popularised the setting.