WASHINGTON — People who want to know more about genetically modified ingredients in their food would be able to get it on some packages, but not others, under a plan the industry is pushing.

Large food companies worried that they might be forced to add “genetically modified” to packaging are proposing voluntary labeling of those engineered foods, so the companies could decide whether to use them or not.

The effort is an attempt to head off state-by-state efforts to require mandatory labeling. Recent ballot initiatives in California and Washington state failed, but several state legislatures are considering labeling requirements, and opponents of engineered ingredients are aggressively pushing for new laws in several states.

Maine and Connecticut have already enacted labeling laws for engineered foods, but they won’t go into effect until other states in the region follow suit.

The industry’s move comes as consumers demand to know more about what’s in their food. There’s very little science that says genetically engineered foods are unsafe. But opponents say there’s too much unknown about seeds that are altered in labs to have certain traits, and that consumers have a right to know if they are eating them. The seeds are engineered for a variety of reasons, many of them to resist herbicides or insects.

Pamela Bailey, president and CEO of the Grocery Manufacturers Association, the food industry’s main trade group, said the decision on labels should rest with the Food and Drug Administration, which is set up to assess the safety of foods.

“It does not serve national food safety policy to leave these issues to political campaigns,” she said.

The grocery manufacturers announced a partnership with 28 farm and food industry groups Thursday to push for the legislation. The groups include the National Corn Growers Association, the National Restaurant Association and the National Beverage Association, all industries that have seen pushback from consumers over modified ingredients.

The groups say mandatory labels would mislead consumers into thinking that engineered ingredients are unsafe.

The state laws could also create a complicated patchwork of labeling laws that would “increase, rather than reduce, consumer confusion,” said Kraig Naasz of the American Frozen Food Institute, another member of the coalition.

The industries are lobbying members of Congress to introduce and pass a bill that would require FDA to create a voluntary label that would take precedence over any state laws. They are also pushing for FDA to do a safety review of new genetically engineered ingredients before they are sold in food. So far, FDA has not found safety issues with modified ingredients.