The lawsuit, filed in federal court in Washington, aims to stop industry leader Monsanto from adding genes to give soybeans, corn and other plants resistance to pests without more rigorous testing.
Monsanto said its products are safe and that the lawsuit was unfounded.
The case comes at a time when Americans have expressed some uneasiness about the rapid increase in transgenic crops and the snack foods, salad dressings and baked goods made from them.
On Monday, the Food and Drug Administration held the last in a series of meetings to hear what changes--if any--are needed in how biotech foods are regulated and labeled.
The issue is also a priority in world trade talks. Japan, the European Union, South Korea and others have already moved ahead to require labels on foods made with transgenic crops to satisfy consumer worries about long-term health and safety.
"This lawsuit alleges that the company had a responsibility to make sure that any safety representations about the product were backed up," said Jeremy Rifkin, head of the Foundation on Economic Trends, which is backing the lawsuit filed by two Indiana farmers, two Iowa growers and a French soybean farmer.
For example, Monsanto should have done additional testing of Bt corn in other countries to determine if the crop posed any risks in other climates and soil types, he said.
"This lawsuit will refocus the global debate," Rifkin said. "It puts the spotlight directly on the life science companies and the future of agriculture. It's no longer just a trade issue between the United States and the European Union."
American farmers, who eagerly embraced biotech crops during the past three years, will spend the winter months deciding what seeds to buy for spring planting. Some are worried that conventional crops could command a premium over transgenic ones, reflecting the preference of overseas buyers.
The lawsuit also accused Monsanto of anti-competitive practices to control the patents and sale of altered seeds. Named in the lawsuit as alleged co-conspirators with Monsanto were Novartis AG, DuPont Co, AstraZeneca Plc., and Dow Chemical Co.
In recent weeks, Monsanto has begun trying to build bridges with European environmentalists, who have been especially worried about long-term health and safety issues. Monsanto Chairman Robert Shapiro pledged in October to discuss biotech crops with Greenpeace and others with a stake in the issue.
The company is also pushing ahead with the next generation of altered crops engineered to benefit consumers.
Last week, Monsanto announced it had developed a genetically engineered rapeseed plant that could help the estimated 800 million people in Third World nations who suffer from blindness and other Vitamin A deficiency diseases.
Rifkin said vitamin-enhanced crops may pose more problems.
"What are the repercussions for foraging birds, insects and other animals when they digest plants that are acting as pharmaceutical factories?" Rifkin said. "We just don't know." q