You’ll really pay extra when you eat at Chipotle, according to its critics.

An aggressive ad campaign against the fast-casual giant says you should cut the fat — warning diners that they could wind up obese like its bare-chested pitchman, whose rolls of fat are anything but appetizing.

The campaign launched in a full-page ad in The Post Thursday, but the big question quickly became who is funding the campaign, which includes a website, Chubbychipotle.com.

Some pundits speculated that a competitor like McDonald’s or Wendy’s might be behind it, but the libertarian-leaning nonprofit claiming responsibility, the Center for Consumer Freedom, said,

“There is no single company or industry paying for the campaign.”

Led by longtime Washington, DC, lobbyist Richard Berman, who also runs public relations firm Berman & Co., the CCF was started in 1996 to take on activists from all walks of life, including the Humane Society of the United States, People for the Ethical Treatment of Animals and even former Big Apple Mayor Michael Bloomberg, who was the force behind the city’s smoking ban and other health initiatives.

The CCF’s beef with Chipotle is the restaurant’s claim of being GMO-free, antibiotic-free and generally a healthier option than other casual restaurants.

“Chipotle is all about marketing itself as a feel-good, healthy company. They are pulling the wool over people’s eyes,” said Will Coggin, the CCF’s director of research.

A Chipotle spokesman described the ad as a “ridiculous smear campaign.”

The controversial CCF is the subject of an exposé website, Consumerdeception.com, which claims that the organization was started with a $600,000 “donation” from Philip Morris and has been known to get funding from Wendy’s, White Castle and Tyson Foods, among other conglomerates.

Sophia Rosenbaum contributed to this report.