EXCLUSIVE

Bethenny Frankel's hugely successful Skinnygirl brand is under attack by a copycat ... according to a new lawsuit.

Frankel's company SG Marks is suing Travis and Stacey Labarge, claiming the couple's Skinnygirl Tea is a rip-off of the real deal. Bethenny's co. says her fame is what drove the brand's success and the Labarges are just piggybacking on her hard work.

SG Marks wants the court to strip the Skinnygirl name from all of the Labarges' products -- and it's also seeking monetary damages.