A bottle of fruit juice is labeled to inform buyers that it is free of GMOs, (or Genetically Modified Organisms), is displayed in Boulder, Colo. (AP Photo/Brennan Linsley)

The political push for labeling genetically engineered foods is spreading across the country. Groups in more than 20 states are organizing local initiatives.

Now Congress could step in, and scuttle all of them.

A bipartisan bill to be introduced today by Rep. Mike Pompeo (R-Kan.) and Rep G.K. Butterfield (D-N.C.) would bar states from requiring the labeling of foods derived from genetically-modified organisms.

The proposed legislation would set up, as an alternative, a U.S. labeling program that would certify foods that are free of genetically modified organisms. But the program would be voluntary, and does not require genetically-modified foods to be labeled.

Butterfield described the bill as a means of keeping food affordable and reducing the confusion that could come from a “50 state patchwork of varying labeling standards.”

Forcing food companies to comply with disparate labeling standards, Butterfield said in a statement, would cause food prices to rise and cost the average family more than $500 a year.

“This bill would provide clear rules for producers and certainty for consumers at the grocery store checkout lane,” Butterfield said.

The bill has support from eight Democrats and nine Republicans, most of them on key committees.

While many scientists believe that genetically modified foods are safe to eat, advocates of GMO-labeling continue to raise questions and argue that at the very least, those who are concerned about safety have a right to know what their food contains. They decried the proposal as another version of what they have called “the DARK Act,” using the acronym for Deny Americans the Right to Know.

Already, three states - Connecticut, Maine and Vermont - have approved legislation that would require that genetically-modified foods be labelled. Similar efforts are under way in several other states. None yet have been put in effect.

“If the manufacturers of these technologies think they are so fantastic, why aren’t they advertising them to the public?” said Heather Spalding,  deputy director for Maine Organic Farmers and Gardeners Association, which pushed the Maine legislation.

She dismissed the argument that the labeling could raise prices.

“They’re just diverting attention from the fact that they want to keep people in the dark,” Spalding said.