Fears that the planting of GM corn in Mexico, where the crop was first developed thousands of years ago, would contaminate indigenous plants led the country to impose a moratorium in 1998, the same year that Europe imposed its own de facto ban.
Allison Snow, co-author of a new report, says that "reliable unpublished data suggests that it is extremely likely that some GM corn is already growing in Mexico, whether it was intentional or not."
Only a handful of countries allow the planting of genetically modified corn, notably the US, Canada, Australia, New Zealand and Japan along with a few others, with the majority resisting the move.
By contrast, combined worldwide production of non-modified maize hit 638 million metric tonnes harvested from 143 million hectares across 150 countries in 2003. The product is grown primarily for its kernel, largely refined into products used in a wide range of food, medical, and industrial goods.
Snow and colleagues on the maize advisory group, established by the North American Commission for Environmental Cooperation (CEC), spent two years studying the potential effects of transgenic - or GM - corn in Mexico, sparked off by concerns over the gene flow from transgenic corn to native Mexican varieties.
The group concluded that genetically engineered corn currently poses no threat to Mexico's native corn varieties, but at the same time cautioned that Mexico should remain vigilant when importing and cultivating corn from the US.
Currently about 30 per cent of corn that Mexico imports from there may be genetically modified, estimates the advisory group.
"To avoid undermining its current moratorium, Mexico should label all corn imported from the US as possibly containing GM seed, or grind the corn when it's imported. Grinding would prevent the imported seeds from being planted," advise the report's authors, along with other recommendations.
But the report, that recommends tougher labelling laws, provoked a vitriolic response from the US government.
"This report is fundamentally flawed and unscientific; key recommendations are not based on sound science, and are contradicted by the report's own scientific findings.
The authors acknowledge that no economic analysis of their recommendations was conducted, and that many of these recommendations are based solely on socio-cultural considerations," said the government in a statement this week.
GM ingredients are regarded with some suspicion by consumers in Europe and as such are used infrequently in food formulations by food manufacturers anxious for buoyant, not falling, sales. But Brussels recently pushed through tough new rules on the labelling of GM ingredients in a bid to make such foodstuffs more accessible to the market.