A genetically modified salmon which grows twice as fast as ordinary fish could become the first GM animal in the world to be declared safe to eat, after America's food-safety watchdog ruled it posed no major health or environmental risks.
The US Food and Drug Administration said it could not find any valid scientific reasons to ban the production of GM Atlantic salmon engineered with extra genes from two other fish species - a decision that could soon lead to its commercial production.
The verdict clears one of the last remaining hurdles for GM salmon to be lawfully sold and eaten in the US and will put pressure on salmon producers in Europe to follow suit.
Supporters of the technology believe GM salmon will make it easier and cheaper to produce farmed salmon, and it could be better for the environment because they can be grown on land-based fish farms.
Sir John Beddington, the chief scientist in Britain, warned two years ago of a "perfect storm" of growing human numbers, climate change and food shortages, where it would be "very hard to see how it would be remotely sensible to justify not using new technologies such as GM".
GM opponents, however, argue that the introduction of the fast-growing salmon creates risks for human health and the environment. They also argue that the salmon will be the start of concerted efforts to create other GM animals for human consumption, which could raise serious questions about animal welfare.
The FDA had indicated the salmon was fit for human consumption. But in a draft environmental assessment written in May and published at the weekend, it went further by declaring that production of the GM fish is unlikely to have any detrimental impact on the wider environment.
Opponents of GM salmon have argued it could escape into the wild, interbreed with wild fish and undermine the genetics of endangered Atlantic salmon.
However, the company behind the GM AquAdvantage salmon said the genetically engineered fish will only be grown as sterile females and kept in secure containers on land.
The FDA agrees that the possibility of GM salmon escaping from fish farms is extremely remote and that interbreeding with wild salmon is equally unlikely.
"[The] FDA has made the preliminary determination it is reasonable to believe that approval of the AquAdvantage salmon NADA will not have any significant impacts on the quality of the human environment of the United States (including populations of endangered Atlantic salmon) when produced and grown under the conditions of use for the proposed action," it concludes.
Peter Riley, of the pressure group GM Freeze, said: "The sterility system does not guarantee that there will be no escapes into the wild and some of them will be fully fertile. It's also debatable whether anyone wants to buy GM salmon, even in the US, if it is properly labelled."
The FDA said the two other US Government agencies responsible for overseeing laws on endangered species - the National Marine Fisheries Service and the US Fish and Wildlife Service - have agreed with the FDA's assessment that there will be "no effect" on wild Atlantic salmon or its habitat.
The steps to engineering GM salmon
1. Chinook salmon - Gene for protein-coding sequence is taken and inserted into the fertilised egg
2. Ocean pout - Gene for antifreeze protein is taken and inserted into the fertilised egg
3. Atlantic salmon - Fertilised egg
4. GM salmon