BERLIN—When it comes to labeling genetically modified (GM) food, the battle lines are usually clear: Those who oppose genetic engineering want it labeled, and those who support it see no need. But today, a group of German scientists and other proponents of GM organisms launched a campaign to require labeling of anything that contains or has been produced with the help of GM organisms.

Their unusual plea is a political gamble; rather than making it more difficult for GM products to reach consumers, they hope the new law will show Germans just how widespread such products already are—whether it’s in food, clothes, drugs, or washing powder—and that there is nothing to be afraid of.

The petition to the German parliament, which will go online tomorrow, asks the German government to prepare a law that requires GM labeling for all food, feed, drugs, textiles, chemicals, and other products that have been produced using genetic engineering. The petition also calls on the government to advocate a similar law at the E.U. level.

The text was written by Horst Rehberger, who leads a group called Forum Grüne Vernunft (Forum Green Reason), and has the backing of several prominent scientists, including Nobel Prize winner Christiane Nüsslein-Volhard, as well as some politicians. If it receives more than 50,000 signatures in the next 4 weeks, the German parliament has to consider the proposal.

Germany already requires GM crops to be labeled as such; the same is true for foods produced directly from them, such as oil made from GM soy beans. Yet many products in which genetic modification played an indirect role require no labeling. Pork can be certified GM-free, for instance, if the animals didn’t eat GM feed in the 4 months prior to slaughter. “The current system is inadequate and sometimes even misleading,” Rehberger says.

Greenpeace and several other environmental groups agree that products from animals raised on GM feed require labeling, but not many other products in which genetic modification played some minor role; that would distract consumers from the real issues, they say. “There is a difference between a piece of tofu produced from 100% genetically modified soy beans and milk from a cow that as a calf received vitamins, one of which was produced with the help of a genetically modified bacterium in a closed system,” says Stephanie Töwe-Rimkeit of Greenpeace in Hamburg. The proposal is designed to negate these differences, making consumer decisions harder instead of easier, she charges.

The proposal does not specify what the labels should look like. Several scientists supporting the petition say labeling needs to be graded, distinguishing for instance whether a product contains GM organisms or has just been processed by them. “I think we just need to be honest and transparent to consumers,” says Wilfried Schwab, a professor of biotechnology of natural products at Technische Universität München.

The proposal is a chance to change the conversation about GM organisms, says geneticist Hans-Jörg Jacobsen, who helped develop pea plants resistant to several fungi. Jacobsen, who retired last year, says his line of research has become all but impossible in Europe; his peas are now being field-tested in Canada. “I think it was a mistake not to label GM food from the beginning,” Jacobsen says.

How consumers would react if GM labels proliferated on supermarket shelves is unclear; there is some research suggesting that they might not be as concerned as genetic modification proponents believe. In one study, consumers in Germany and five other countries were offered three options at a fruit stall: “organic,” “conventional,” and “spray-free genetically modified” fruit. When prices were the same, one-fifth of the consumers opted for GM fruit. Modeling suggested that if GM fruit was sold at a 15% discount and organic fruit at a 15% premium—which the authors say is most likely—GM products would get more popular; in three countries, including Germany, they might even have the highest market share.

With time, a GM label could even become a positive sign, Jacobsen says, just like “Made in Germany,” which was originally introduced in Great Britain to mark inferior import products. “Look how that turned out,” he says.

*Correction, 19 May, 7:43 a.m.: An earlier version of this story stated that pork can be certified GM-free if the animals didn’t eat GM feed in the 6 weeks prior to slaughter; 6 weeks has been changed to 4 months.

*Update, 19 May, 8:08 a.m.: The petition is now online here.