Organic food from China, like tea and frozen broccoli, has increasingly found its way onto American store shelves, typically emblazoned with the green “U.S.D.A. organic” seal also found on food grown in this country.

The federal certification, the backbone of the organics industry, is aimed at assuring consumers that farmers and food manufacturers have passed tough, independent inspections – even half a world away.

Now serious questions about certification in China have been raised by the United States Agriculture Department. The agency, which uses private groups to conduct most organic inspections worldwide, has banned a leading American inspector from operating in China because of a conflict of interest that strikes at the heart of the organics’ guarantee. The federal agency also plans to send an audit team to China this year to broadly review the certification process.

Federal officials say the banned inspector, the Organic Crop Improvement Association, used employees of a Chinese government agency to inspect state-controlled farms and food processing facilities. The group, based in Nebraska and known by the initials O.C.I.A., has for years been one of the leading inspectors of Chinese organics for the United States market. Anticipating the department’s action, the group shut most of its operations last year.

The ban, to be formally announced on Monday, is likely to propel consumer worries about organic food from a country that many associate with food safety scandals and lax regulation, involving things like contaminated milk and toys coated in lead paint.

Whole Foods Market, the nation’s leading organic retailer, has used Chinese organics, including those from association-inspected producers, in many of its store brand products, including frozen vegetables, sunflower seeds, pine nuts and bottled teas.

But the number of those products has been shrinking, in part because of consumer worries about their credentials as organics. Two years ago, the company said, it sold about 30 private label items with organic ingredients from China; by the end of this year, it will stock only two: shelled and unshelled frozen edamame soybeans.

“Over the years, we’ve gotten a lot of critical feedback from customers on products that we source from China,” said Errol Schweizer, Whole Foods’ senior global grocery coordinator.

Whole Foods said it had conducted its own audits of its Chinese suppliers and had tested their products for contaminants and was confident that edamame soybeans remained of high quality and a good value. The retailer said it had also found some similar products from places besides China at better prices.

The United States imports $3 billion a year in farm products from China. Trade data does not single out organic farm products, which are believed to account for a small but growing portion of the total. The upward trend can be seen in the number of Chinese organic producers certified under Agriculture Department rules, which rose more than 200 percent, to 669 last year, from 216 in 2008. China is one of the biggest exporters of agricultural products to the United States.