A Sonoma County animal defense fund on Monday filed a class-action lawsuit against a Petaluma egg farmer, alleging his cartons falsely lead consumers to conclude that his chickens roam freely around the farm.

The Animal Legal Defense Fund is seeking both unspecified monetary damages and an order forcing the Petaluma Egg Farm to change its cartons.

The lawsuit alleges that cartons for the farm's Judy's Family Farm brand depict hens in an outdoor environment, when the cage-free birds actually are confined in immense chicken houses. It cites one carton that says the hens "are raised in wide open spaces in Sonoma Valley, where they are free to &‘roam, scratch, and play.'"

The images and statements "are objectively false and are likely to induce reasonable customers to purchase Judy's Family Farm Eggs by appealing to their concerns about animal welfare," according to the lawsuit filed in Alameda County.

It was the first time in its 33-year history that the Cotati-based defense fund had sued a Sonoma County business.

Steve Mahrt, the farm's owner, was unavailable for comment Monday.

Previously, Mahrt has defended his operation from critics who questioned whether he should keep organic certification for part of his operation.

Last year at one farm he showed a reporter a screened, barracks-like building containing 13,000 hens. He maintained the unusual design allowed hens to scratch inside and receive natural sunlight and fresh air, as opposed to enclosed structures that require fans and artificial light.

"What I'm doing is what I think is the safest system for our consumers and for our hens," he said.

Christopher Berry, the lead attorney for the defense fund, said the nonprofit this year also sued over foie gras farming in New York State and urged federal regulators to stop tuna processors from misleading consumers regarding the effect of their harvests on dolphins.

What's common among the cases, said Berry, is that consumers face "smoke and mirrors from the industry who want to exploit their conscientious decisions."