Food companies would not have to disclose whether their products include genetically modified ingredients under legislation passed by the US House of Representatives on Thursday.

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

There is little prospect of the measure becoming law soon because there is no companion legislation in the Senate although one senator said he is working on it.

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 labelling 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.

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 labelling, but those measures don’t take effect unless neighbouring 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.

“The reality is, biotechnology has time and time again proved safe,” the Bill’s sponsor, 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 criticise 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 per cent to 80 per cent 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 labelling 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 labelled 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 labelling 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, said on Wednesday in a speech opposing the Bill that he buys genetically modified foods but thinks it should be a choice.

Michael Gruber of 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.”