Heather Thompson; Sara Blakely Credit: Craig Barritt/Getty; Ben Rose/Getty

Her line of shapewear may smooth your lines, but Yummie Tummie founder Heather Thomson has no plans to smooth things over with Spanx founder Sara Blakely.

The Real Housewives of New York star is accusing Blakely — who Forbes calls "the world's youngest self-made female billionaire — of infringing on her patents for Yummie Tummie's control tops. Thomson was first made aware of the issue, she told WWD, when a package arrived at her offices bearing a Spanx control tank top and an anonymous note saying they were being sold on QVC.

"I immediately recognized it as my original Yummie Tummie tank," Thomson told the trade. Spanx, via a declaratory judgment they filed, claims their products do not infringe on Yummie Tummie's patents.

Thomson said the battle of the bulge-fighters isn't over. "I hope she's ready for war because I will not lie down," she declared.

Spanx's estimated annual wholesale revenue is between $225 million and $240 million; Yummie Tummie's estimated retail sales are $60 million.

Interestingly, fellow Real Housewife of New York Jill Zarin also designs a line of shapewear, Skweez Couture, which launched in 2011.