Rival Underwear Makers Butt Heads

March 14, 2013 -- Rival underwear-makers Spanx and Yummie Tummie are butting heads, the latter claiming patent infringement, the former denouncing that claim as without merit.

The dispute pits one diva against another: Heather Thomson, a former cast member of hit TV show "Real Housewives of New York," founded Yummie Tummie in 2008, introducing the company's signature, shape-flattering 3-panel control top. Sara Blakely—youngest woman on Forbes' billionaires list—founded Spanx in 2000, introducing what Spanx calls a shaping camisole in 2005.

Both companies produce elasticized garments that do for today's women what girdles and corsets did for those bulges of yesteryear.

Thomson told Women's Wear Daily she received earlier this year from an anonymous sender a package that contained several of Spanx's control-tops. "I immediately recognized [them] as my original Yummie Tummie tank," she told WWD. She told the publication that she fired off a letter of complaint to Spanx on January 18, telling them they were violating Yummie Tummie patents and to cease manufacture of the items.

A request from ABC News for further comment from Thomson and Yummie Tummie received no reply.

Spanx, in response to the January 18 letter, filed on March 5 a complaint for declaratory relief through its Atlanta law firm, King & Spaulding. That complaint asks the court to declare Spanx not to be in infringement of Yummie Tummie's patents and to award Spanx expenses and attorneys' fees.

The complaint quotes Yummie Tummie's January 18 letter as accusing Spanx of making and selling shapewear product that contain Yummie's patented designs. These products, the complaint further quotes Yummie's letter as saying, "appear substantially the same as the patented designs from the point of view of an ordinary observer, thereby constituting design patent infringement." It specifies three Spanx products in particular, which it refers to as "the Accused Products": Spanx's Total Taming Tank, Top This Tank and the Top This Cami.

A spokesperson for Spanx, via email, tells ABC News that Spanx was first to market shapewear. "Spanx," says the email, "has had countless imitators through the years. Anyone can make a claim, but it doesn't mean it has merit. Spanx has not infringed on any valid patent."

Women's Wear Daily quotes Thomson as not just refusing to relent, but as throwing down the rubber gauntlet: Yummie Tummie, she declares, "will not scream uncle." Further: "I hope [Blakely]'s ready for war because I will not lie down."