WASHINGTON -- Food companies would not have to disclose whether their products include genetically modified ingredients under legislation passed by the House Thursday.

The House bill is backed by the food industry, which has fought mandatory labeling efforts in several states around the country. The legislation, which passed 275-150, would prevent states from requiring package labels to indicate the presence of genetically modified organisms, or GMOs.

So far, Vermont is the only state set to require the labels. That law will take effect in July 2016 if it survives a legal challenge from the food industry. Maine and Connecticut have also passed laws requiring the labeling, but those measures don't take effect unless neighboring states follow suit.

The country's largest food companies say genetically modified foods are safe and that labels would be misleading. They say a patchwork of laws around the country would be expensive for companies and confusing for consumers.

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"The reality is, biotechnology has time and time again proved safe," the bill's sponsor, Kansas Republican Rep. Mike Pompeo, said on the House floor. "We should not raise prices on consumers based on the wishes of a handful of activists."

Advocates for the labels say people have a right to know what is in their food and criticize the legislation for trying to take away states' ability to require the labels.

"What's the problem with letting consumers know what they are buying?" asked Vermont Rep. Peter Welch, a Democrat.

Genetically modified seeds are engineered in laboratories to have certain traits, like resistance to herbicides. The majority of the country's corn and soybean crop is now genetically modified, with much of that going to animal feed. It also is made into popular processed food ingredients like high-fructose corn syrup, corn starch and soybean oil.

The food industry says about 75 percent to 80 percent of packaged foods contain genetically modified ingredients.

The Food and Drug Administration has said GMOs are safe, and the federal government does not support mandatory labels. Even so, the House bill would make it harder for the agency to require labeling nationally by laying out additional standards for such a policy.

At the same time, the legislation would step up FDA oversight by requiring that any new genetically engineered products be reviewed by the agency before they can be sold. That process is now voluntary for most modified foods.

The bill would also create a new certification process at the Agriculture Department for foods that are labeled free of GMOs. That would mean anyone wanting to use that label would eventually have to apply. Organic foods would be automatically certified, since they are already required to be free of engineered ingredients.

A December Associated Press-Gaff poll found that two-thirds of Americans support labeling of genetically modified ingredients on food packages.

Many of those who support the labels say they have no problem buying food containing GMOs, but they think there should be more accountability in the food industry. Rep. Jim McGovern, D-Mass., said Wednesday in a speech opposing the bill that he buys genetically modified foods but thinks it should be a choice.

Michael Gruber of the Grocery Manufacturers of America, the industry group leading the fight against mandatory labels, says those who want the labels are trying to scare people away from genetically modified foods. "This is to tear down brands in the name of right to know," Gruber said.

There is no similar bill in the Senate, although Sen. John Heaven, R-N.D., has said he is working on legislation.

It's unclear whether President Barack Obama would sign the legislation. Agriculture Secretary Tom Vilsack has been supportive of genetically modified crops and has praised voluntary labeling solutions like special bar codes on packages to allow consumers to access information via smartphone. But the White House has so far been silent on the House bill.

Vermont Gov. Peter Shumlin said after the vote that people who want to know what's in their food will eventually win the fight.

Americans "are demanding the right to know what's in their food," Shumlin said.