WASHINGTON — The organic food industry is gaining influence on Capitol Hill, prompted by its entry into traditional farm states and by increasing consumer demand.

Tensions between conventional and organic agriculture boiled over last week during a late-night House Agriculture Committee debate on farm legislation that for decades has propped up traditional crops and largely ignored organics.

When Rep. Kurt Schrader, D-Ore., a former organic farmer, offered an amendment to make it easier for organic companies to organize industry-wide promotional campaigns, there was swift backlash from some farm-state Republicans. One lawmaker complained about organics’ “continued assault on agriculture.”

“That’s one of the things that has caught me and raises my concerns, is that industry’s lack of respect for traditional agriculture,” said Rep. Austin Scott, R-Ga. He was referring to some organic companies’ efforts to reduce the number of genetically modified crops in the marketplace.

At the same time, Scott acknowledged that he and his wife buy organic foods.

Growing consumer interest in organics has proved tough for some Republicans on the committee to ignore. Eight Republicans, most of them newer members of the committee, joined with all of the committee’s Democrats in supporting the amendment, which was adopted 29-17.

Rep. Vicky Hartzler, a Missouri Republican who owns a farm equipment business and a corn and soybean farm, said she supported the amendment not only because helping organics is good for agriculture but because many of her constituents eat organic foods.

The amendment would allow the organic industry to organize and pay for a unified industry promotional campaign called a “check-off” that is facilitated by the Agriculture Department but is no cost to the government.

Laura Batcha of the Organic Trade Association says one reason the industry would approve a campaign is that many organic producers are concerned that consumers don’t understand that products labeled “natural” aren’t necessarily organic, which requires certification.

The organic industry has exploded in the past decade, with $35 billion in sales and 10 percent growth last year. There are more than 17,000 organic businesses in the U.S.

Organic products are required to be certified by the USDA and are grown without pesticides and genetically modified ingredients, mainstays of traditional agriculture.

Government-managed promotional check-off programs such as the one that would be allowed under the amendment are required to be positive and not disparage other products. Some lawmakers seemed wary that such a campaign would be possible.

“How do I present organic pork without disparaging nonorganic pork?” asked the House committee chairman, Rep. Frank Lucas, R-Okla., who opposed the amendment.