The Brazilian government’s decision to order labels to be put on all genetically modified foods has met with criticism on both sides of the GM debate.

On Monday the government published a decree mandating the labelling of all foods and food ingredients made up of more than 1% genetically modified material. The decree is part of the government’s attempt to end Brazil’s large black market in illegal GM soy planting, reported Reuters.

One of the decree’s critics, Leila Oda, who is the president of the National Biosecurity Association, said the decree did not make clear what standards would be used to determine levels of GM content. She added that there would be no way of detecting GM ingredients in meat from animals that had been fed biotech corn or soy.

At the other end of the GM debate, consumer watchdog Idec said the decree was a step forward but added that it doubted whether the decree did enough to protect consumers. Idec said consumers would not know if unlabelled food was totally GM-free. It also added its concerns that no labelling would be required if GM ingredients were undetectable after processing.

“This means all highly processed products (such as crackers, chocolates, pastas) will not be labelled, by the simple fact of destroying the protein making it impossible to detect GM,” the institute was quoted as saying by Reuters.