Jessica Simpson was spotted wearing a T-shirt with the slogan "Real Girls Eat Meat" printed across her chest — leading PETA to denounce the singer as a "stupid girl."

On the PETA Files blog, the animal rights group responds to the Simpson shirt by listing the "top five reasons that only stupid girls brag about eating meat."

Click here for PETA's top five reasons.

Simpson family insiders reportedly told OK! magazine that the shirt is a dig at her boyfriend Tony Romo's ex-girlfriend, country superstar Carrie Underwood — who doesn't eat meat. PETA twice has named Underwood the "World's Sexiest Vegetarian."

Click here to see Jessica wearing the shirt.

"Jess is sick of hearing about how Tony still has feelings for Carrie," the insider told OK! "She's obviously trying to poke fun at her rival and let her know who really has Tony's heart."

PETA released the following statement to OK!:

"Jessica Simpson's meaty wardrobe malfunction makes us thankful that no one is looking to her for food advice. Chicken-of-the-Sea, anyone? The woman who thought that Buffalo 'wings' came from buffalos would benefit from some good veggie brain food."

Meanwhile, Simpson was mistaken for Underwood following lunch with pals at Dos Caminos in NYC’s SoHo on June 11, OK! reports.

Jess, 27, returned to her hotel, where a girl asked for her autograph.

"She said she was her No. 1 fan from back in the 'Idol' days," an eyewitness tells OK! "Jessica smiled politely and didn’t correct her, and she started to laugh when the girl asked how she was doing since her devastating split from Chace [Crawford]."

Jess took it all in stride, but according to OK! a pal said: "She wasn’t pleased that the girl had no clue who she was!"

Click here for the OK! report.