While most consumers’ image of Costco involves people stocking up on cases of ketchup, toilet paper, and bottled water, the warehouse retailer does sell some high-end jewelry and accessories. But the folks at Tiffany & Company claim the “Tiffany” rings that were being sold at Costco were anything but.

According to the complaint [PDF] filed yesterday in a U.S. District Court in New York, a customer was shopping at a California Costco last November when she saw that the store was selling what it advertised as “Tiffany” diamond engagement rings ranging in price from $3,199.99 to $6,399.99.

When Tiffany learned of this, it says the company investigated and determined that these rings were not “manufactured by, approved by, licensed by, or otherwise in any way properly associated with Tiffany.”

Tiffany contacted Costco, which subsequently removed any signage indicating that these rings were related to Tiffany & Co.

“Unbeknownst to Tiffany, Costco had apparently been selling different styles of rings for many years that it has falsely identified on in-store signage as ‘Tiffany’,” reads the complaint, which alleges that Costco unlawfully traded off Tiffany’s good will and brand awareness. “There are now hundreds, if not thousands, of people who mistakenly believe they purchased and own a Tiffany engagement ring from Costco.”

The lawsuit alleges trademark infringement, counterfeiting, unfair competition, injury to business reputation, false advertising and deceptive business practices.

And just because some of you are already humming it, here it is… the worst song of the last 30 years:

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