The growth of genetically-modified crops has dipped for the first time following two decades of steady increases, according to a study released Wednesday.

Twenty years after the first genetically-modified plant was marketed, the worldwide acreage of GM crops reached 181.5 million hectares in 2014.

But after 19 years of annual increases, the area planted with biotech seeds fell by one percent last year, according to the pro-GM International Service for the Acquisition of Agri-biotech Applications (ISAAA).

The group blamed the slowdown on the collapse of commodity prices including corn and cotton.

"ISAAA anticipates that total crop hectarage will increase when crop prices improve," the organisation said in a press release.

The United States, the world's leader in GM foods, saw a 2.2 million hectare decline in farmland given over to genetically modified crops in 2015.

In South Africa, severe drought reduced acreage of GM corn from three million hectares to 2.3 million hectares last year.

And last week Burkina Faso abandoned its genetically modified cotton crop altogether, saying the project was not profitable.

The ISAAA said that despite challenges, the area devoted to GM crops has "increased 100 times" in the past 20 years and now involves 18 million farmers in 28 countries.

From 1996 to 2014, biotech crops have successfully been grown on a cumulative area of 1.8 billion hectares.

Five developing countries -- Brazil, Argentina, India, China and South Africa -- grew almost half of all GM crops in 2015.

GM remains hugely controversial in many countries, stirring sharp debate over the crops' use and impact.

The ISAAA said opponents of GM were "opposed to science/evidence-based regulation" and that demands for "onerous" regulation would hurt poor farmers in developing countries.