Red Robin's latest ad may have offended about 13 percent of the U.S. population.

The commercial begins by promoting fast food restaurant Red Robin's 24 different burger options, before the actress in the commercial says in a mock whisper: "We even have a garden burger just in case your teenage daughter is going through a phase."

While this was most likely meant to be nothing more than a light-hearted joke, vegetarians across the United States were not laughing.

People for the Ethical Treatment of Animals (PETA) released an official statement on the commercial: "Thirteen percent of the U.S. population now identifies as vegetarian or vegan [according to Public Policy Polling], which is one reason why more and more burger joints and other restaurants continue to add a wider variety of vegetarian and vegan dishes to their menus, including Red Robin, Johnny Rockets, Fuddruckers, Smashburger, and Denny's."

"PETA is thrilled that Red Robin has veggie burgers, and we agree with the many comments that the one-liner in the commercial is a bit outdated," it added.

According to Yahoo! Shine, recent surveys have found that about 5 to 13 percent of Americans are vegetarians. That is equal to at least 15 million people that the commercial may have alienated with its jab.

"Though I applaud any fast food chain that offers a veggie burger, and I hope that more do, the idea that not eating animals is reserved solely for teenage girls going through a phase is obviously meant to insult both vegans and girls," Jasmin Singer, executive director of Our Hen House, a New York-based multimedia vegan activism organization, told Yahoo! Shine. "Why is Red Robin insulting the very customers it's reaching out to?"

Kevin Caulfield, Red Robin's senior director of communications, told The Huffington Post: "the intent of the ad was to remind our guests again that Red Robin serves meatless options too." The Gardenburger and the BOCA Original Vegan Burger have been on Red Robin's menu for years, he added.

On Tuesday, Red Robin told its vegetarian customers it was sorry. "If anyone was offended by the ad, we sincerely apologize," Caufield told Yahoo! Shine. "We value all our guests, including those who want vegan and vegetarian options."

Caufield added that the commercial "was intended to increase awareness of these vegetarian options in an irreverent, lighthearted way."

Watch the ad below: