The corn or maize has been genetically modified to include an insecticide designed to kill corn rootworm and to ensure higher crop yields.
It was developed by U.S. biotech company Monsanto and approved for human consumption by the EU in January 2006.
But the study, carried out by French researchers from the Committee for Independent Research and Genetic Engineering, has raised serious concerns about its safety.
The team, based at the University of Caen, fed the corn, called MON863, to rats for three months. They found signs of toxicity in the liver and kidney of the rats, along with changes in weight between the sexes.
Male rats were found to have lost on average 3.3% of their body weight, while females gained 3.7%.
Professor Gilles Eric S»ralini, who led the team, said, "Our counter-evaluation shows that there are signs of toxicity. Nobody can say scientifically and seriously that consumption of the transgenic maize MON863 is safe and good for health."
The study was commissioned by Greenpeace, which is among a number of environmental groups opposed to GM farming.
It has now called on food health authorities to withdraw the corn from sale. A spokesman said, "It is the first time that independent research, published in a peer-reviewed journal, has proved that a GM organism authorised for human consumption presents signs of toxicity."
A spokesman for Monsanto said, "All the experts agree that the maize in question is as safe as traditional maize."
Green campaigners, including Friends of the Earth, have renewed calls for field trials of a GM potato to be scrapped.
BASF's blight-resistant potatoes are due to begin their UK tests this spring at two locations ñ a research centre in Cambridge and a site in Yorkshire.
A Dutch court has already blocked a trial of the same potato crop.
From the March 26, 2007, Prepared Foods e-Flash