NEW YORK » Campbell Soup says it now supports mandatory national labeling for products containing genetically modified ingredients, and that it will stop backing efforts opposing such disclosures.

The change of heart by the maker of Pepperidge Farm cookies, Prego sauces and Spaghetti-Os marks a break from industry groups that have sought to make labeling voluntary.

About three-quarters of Campbell’s products contain GMOs. The company has opposed a patchwork of state-by-state legislation that it believes would confuse customers.

States have tried to address the issue on their own and Vermont passed legislation requiring labeling of genetically modified ingredients on certain products by July. But industry groups want to pre-empt such efforts with federal legislation that would make disclosures voluntary, said Michele Simon, a public health lawyer.

“They’re going for as little as they can,” Simon said.

If a federal labeling standard isn’t established in a “reasonable amount of time,” Campbell says it will work independently to disclose the presence of GMOs in its products. The company did not specify a timeline for doing so.

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. Corn and soybeans are also made into popular processed food ingredients like high-fructose corn syrup, corn starch and soybean oil.

The food industry says about 75 to 80 percent of foods contain genetically modified ingredients. The Food and Drug Administration has said that GMOs are safe.

Still, the number of products stamped with a voluntary “non-GMO” label from a third-party group has proliferated as the issue has gained attention. The label, which is displayed on the front of packages, has become a marketing tool in some cases.

Campbell is also calling on the federal government to propose a national standard for “non-GMO” claims made on food packaging.

The company’s disclosure of GMO ingredients likely wouldn’t be as prominent as the “non-GMO” labels displayed on some products. An image provided by Campbell to illustrate compliance with the Vermont law showed the back of a Spaghetti-Os can with the words “Partially produced with genetic engineering” in small print at the bottom.

The change in position by Campbell comes amid dimming prospects for industry-backed legislation that would prevent states from requiring GMO labeling.

Last month, the industry made an aggressive push to add the federal legislation to a massive year-end spending bill in December, but failed to win enough support. That may have been its best bet before Vermont’s law is enacted, although lawmakers say they will keep trying in the coming months.

Campbell Soup CEO Denise Morrison has been outspoken about the need for big food makers to adapt to changing tastes. The company, based in Camden, N.J., has been diversifying its packaged food lineup with offerings that are seen as fresher.

Its acquisitions in recent years include premium juice and carrot seller Bolthouse Farms and Plum Organics, which makes baby food.

In a message posted online by Campbell today, Morrison stressed that the company is in “no way disputing the science GMOs or their safety.” But she said GMOs have become a top issue among consumers.

“We have always believed that consumers have the right to know what’s in their food,” Morrison wrote.

AP Writer Mary Clare Jalonick contributed from Washington.