(WARSAW) - Global environmental watchdog Greenpeace launched a new report Monday warning the European Union against authorising herbicide-tolerant genetically engineered (HTGE) crops, saying they would lead to herbicide-resistant super-weeds.

"When herbicide-tolerant crops are relied on heavily, they trigger the spread and emergence of resistant weeds, which has now happened throughout the United States," said Oregon-based agricultural economist Charles Benbrook, who was commissioned by Greenpeace to study the issue.

"Then farmers have to spray much more heavily, turning to older, higher-risk herbicides which increases risk to both their cost of production as well as the public health problems associated with herbicide use," Benbrook told AFP, adding: "We're solidly in that phase in the US."

The launch of the report in Warsaw, Poland comes as the 27-member EU considers authorising 26 genetically engineered crops, including 19 that are tolerant to herbicides, Greenpeace said.

Benbrook has predicted EU farmers risk using up to 15 times more glyphosate-type herbicides on HTGE corn, soy and sugar beet crops to stem the growth of super-weeds over a 14-year period (2012-2025), as well as inflated prices for genetically modified seeds, should Brussels allow them.

Greenpeace commissioned Benbrook to complete a study on glyphosate-tolerant crops in the EU based on data on use of the herbicides in the US.

US biotech giant Monsanto brought glyphosate to the market in the 1970s under the Roundup trademark, but it is now off-patent and has become the most commonly used herbicide in the US.

While its producers claim glyphosate has relatively low toxicity compared to other herbicides, concerns persist about its environmental and human impacts.

"If EU farmers take up HTGE technology as quickly as in the US, glyphosate use in maize crops -- the most important and widely grown crop in Europe - will increase by over 1,000 percent by 2025 over current use, and total herbicide use will double," Greenpeace warned in a Monday statement quoting the Benbrook study.

Benbrook and two US farmers are on an 18-day Greenpeace tour of Europe to meet farmers, local communities and politicians to share their concerns about HTGE crops.

Greenpeace campaigner Lasse Bruun also unveiled the YouTube launch of "Growing Doubt" (http://www.youtube.com/watch?v=CNxhw2jiDtA&noredirect=1), a Greenpeace documentary focused on the experience of farmers in the US and Argentina with HTGE crops and glyphosate-based herbicides.

It comes on the heels of the "Bitter Seeds" documentary focused on an epidemic of farmer suicides in India among peasants who have lost their land after falling into debt using genetically modified crops.