Most of the corn and soybeans grown in the U.S. is genetically engineered. A new bill would prevent states and local governments from requiring food labels to disclose such ingredients. (Jim Young/Reuters)

A fierce food fight has erupted in Congress over the labeling of genetically engineered foods.

At the center of the conflict is a bill sponsored by Rep. Mike Pompeo (R-Kan.) that would block state and local laws from requiring food labels to disclose genetically engineered ingredients.

Vermont, Connecticut and Maine have passed mandatory labeling laws for genetically modified food. At least 15 other states are considering similar regulations.

Pompeo’s “Safe and Accurate Food Labeling Act” would nix those laws and instead set up a voluntary nationwide labeling system overseen by the federal government.

The bipartisan bill has become the latest battleground over the use of genetically modified organisms, or GMOs, in the U.S. food supply. GMOs have been around for 20 years. About 90 percent of the corn, soybeans and cotton grown in the United States is genetically engineered, meaning that the crops have been artificially altered to use less water or resist pests.

The American Association for the Advancement of Science, the American Medical Association and the World Health Organization have said that all GMOs on the market are safe. So has the federal government.

But as consumers grow increasingly concerned about what is in their food — from antibiotics and hormones to additives and trans fats — pressure is mounting on the food industry and producers to be more transparent.

Consumer groups warn that Pompeo’s bill would rob Americans of their right to know what they are eating. They launched a nationwide campaign against the legislation, renaming it the Deny Consumers the Right to Know Act, or Dark Act.

Pompeo, a conservative lawmaker from Wichita, says the scientific consensus that GMOs are safe makes mandatory state and federal labeling unnecessary.

“If we allow states to continue to irrationally produce laws that require a completely safe food to contain labels,” he said in an interview, “we risk raising the cost of food on those who can least afford it.”

Pompeo says that food prices would spike if producers had to comply with dozens of different sets of laws that varied from state to state and city to city.

For now, there are no government-approved labels to let consumers know which foods are derived from GMOs.

Many companies advertise their food as “Non-GMO” through the Non-GMO Project, a private nonprofit started by retailers. The group uses testing and product segregation practices to verify that products with its butterfly seal contain fewer than 1 percent GMO ingredients.

Companies such as Ben & Jerry’s ice cream and Chipotle Mexican Grill have responded to the consumer concerns about GMOs by removing genetically engineered ingredients from their food. The companies still serve dairy and meat products from animals that eat at least some genetically engineered feed, however.

People who want to be sure to avoid food derived from GMOs can buy organic. Organic foods, which must be certified by the Agriculture Department, cannot by law contain genetically engineered ingredients. But an all-organic diet can be prohibitively pricey.

Consumer advocates say the lack of a government-mandated label for GMOs leaves many American shoppers confused.

“This fight is really a referendum on whether or not people should have basic information about their food and how its grown — and whether that information should be included on the food package,” said Scott Faber, vice president of government affairs for the nonprofit Environmental Working Group, an environmental and health advocacy organization that opposes Pompeo’s bill.

More narrowly, Faber said, it’s a debate over whether states can use their authority to provide basic information about food on the package.

Pompeo counters that his bill doesn’t infringe on state’s rights any more than Federal Aviation Administration rules do.

“We don’t let every state set their own rules for air traffic safety,” he noted.

“This is classic interstate commerce,” he added. “The founders understood that if we were going to have effective trade between the states that we couldn’t let cities and counties and states erect irrational protectionist barriers, and that’s what these laws are.”