(Photo Credit: Susan Walsh/AP Photo

Lobbying usually doesn't come with a side of ice cream.

But Ben & Jerry's co-founder Jerry Greenfield brought some with him to Capitol Hill today, where he joined Rep. Peter DeFazio to advocate for mandatory labeling of genetically modified food.

"One spoonful at a time will change the law," DeFazio, D-Ore., proclaimed.

DeFazio and Greenfield appeared with pro-labeling advocates to protest a bill proposed by House Republicans that would make labeling genetically modified food voluntary.

"Companies should be proud to talk about the ingredients they put in their food," said Greenfield, whose ice cream company is known for their inventive flavors and ingredients. "This is as mainstream of an idea as you can get."

The bill, authored by Rep. Mike Pompeo, R-Kansas, would nullify efforts in several states to require GMO labeling; initiatives he called "misleading" in a Kansas newspaper op-ed.

"Not a single credible scientific study has shown [genetically modified food] to be anything but 100 percent safe. We should follow the science and make policy accordingly, rather than follow political agendas," Pompeo wrote.

Citing the early medical consensus on the health benefits of cigarettes, DeFazio said that the lack of evidence doesn't disprove any undiscovered health risks genetic modification might have.

"When's the last time a tomato plant mated with an arctic char? This hasn't happened in nature before," he said.

Greenfield, who put Ben & Jerry's on the map with iconic flavors and creative ingredients, has supported state-level efforts to mandate labeling. The company renamed its chocolate brownie flavor to "Food Fight Fudge Brownie" in support of a legal fund to defend Vermont's first-in-the-nation GMO labeling law that is being challenged in court. (Event organizers passed out ice cream cups of the flavor after the news conference.)

Ben & Jerry's, which Greenfield and his partner Ben Cohen sold to Unilever in 2000, supports a number of progressive political causes, including climate change and same-sex marriage. In 2012, Cohen founded Stamp Stampede, an organization geared toward limiting the influence of money in politics.