New guidelines aimed at regulating the production of genetically-modified animals destined for human consumption have been issued by regulatory authorities in the US.
The guidelines aim to set out clearly how the US Food and Drug Administration (FDA) intends to regulate meat, diary products and other foods which originate from genetically-modified animals.
The draft rules, which seek to address concerns about such products dubbed "frankenfoods," will be opened up to public and professional comments for the next 60 days before coming into effect.
"Genetically engineered animals hold great promise for improving human medicine, agriculture, the environment and the production of new materials," said deputy commissioner Randall Lutter.
"The FDA has long been involved in their scientific evaluation," Lutter said. "Our guidance provides a framework for both GE animals and products made from them to reach the market."
But consumer protection organizations condemned the draft rules, noting that the FDA was not imposing a labelling system to say where the products originate from.
"It is incomprehensible to us that FDA does not view these animals differently from their conventional counterparts," said Jean Halloran from the Consumers Union.
"In our view, consumers have a right to know if the ham, bacon or pork they are buying come from pigs that have been engineered with mouse genes."
Michael Hansen, also from the Consumers Union, said animals that have been genetically engineered can contain genes from completely different species.
Mouse genes may be inserted into pigs to help them process phosphorous more efficiently, or spider genes could be put into goats to make them produce silk in their milk, he said.
Some saw the FDA draft guidelines as a first step as the agency navigates its way through this controversial area of biotechnology.
"Although the FDA's announcement is a good first start, it does not address the risks that GE animals might pose to the environment," said Gregory Jaffe from the Center for Science in the Public Interest.
"Would it be the FDA that would determine whether fast-growing genetically engineered salmon would endanger native salmon populations?" he asked.
Genetic engineering can help ensure that fish grow bigger more quickly, or create animals which produce in their blood or milk substances which can be used to make medicines.
Such techniques, under which a plant or animal's existing DNA is mixed with the DNA of another organism, are already common in agriculture to render crops more resistant to insects or drought.
This is different to cloning in which the scientists create the exact double of an animal or organism.
The FDA and its European counterpart in January approved the sale of meat and diary products coming from cloned animals, judging they posed no risks to humans.