Battle of the Bootays

8/31/2006 11:00 AM PDT

The rivalry between Jessica Simpson and Vanessa Minnillo just got a whole lot sexier.

TMZ has learned Jessica recently stopped into Linda's lingerie store in Soho, along with an entourage of 2 girlfriends and one beefy bodyguard. After perusing the unmentionables for over 30 minutes, Jessica finally settled on 3 pairs of hot ruffled knickers ... but not just any knickers.

The aforementioned underwear were exact replicas of the Spoylt lingerie products worn by Nick Lachey's new lady, Vanessa Minnillo, in her famous Maxim Magazine spread. Hmmm ... does Jessica have something to prove??