The website, which advertises a vegetarian food range, said: "Exciting new fish range in stores now. We're doubly excited this month.
"Not only can we announce our new fish range, but we might also put an endangered meal back on the menu. You know what they say. 'Plenty more fish in the sea' Or are they?"
"Popular fish like cod and tuna are endangered by overfishing. And sustainable alternatives, like pacific cod, are a bit heavy on the food miles. So, never ones to shy away from a global challenge, Quorn brings you fish, but without the fish-in."
Further text stated: "Tuck into classics including Fish-less Fingers and Tuna Style and Sweetcorn Crispbakes.
"They're full of flavours, a source of protein, and the Fish-less Fingers are enriched with healthy omega 3.
"Oh, and all with 0% fish. The ultimate meal is back. Which brings us to that endangered treat: the fish finger sandwich. Now, reinstated as comfort food with a conscience, bring the Fish-less Finger butty."
The Seafish Industry Authority challenged the ad on three counts. Firstly, it challenged whether the claim that cod and tuna were endangered species was misleading and could be substantiated.
Secondly, the ad misleadingly implied Quorn's fish range offered the same benefits of omega 3 found in oil fish.
And finally the ad misleadingly implied Quorn's fish range offered the same general health benefits as fish.
On the first point, Quorn defended itself by while admitting that not all species of cod and tuna were classed as endangered by the International Union for Conservation of Nature (IUCN), some were classed as vulnerable or endangered.
On the second point, Quorn asserted that the omega 3 in its Fish-less Fingers was in the form of DHA (docosahexaeonic acid), a long chain form of omega 3, also found in fish.
And thirdly, it said it was unavoidable that consumers would compare their "fish range" to fish, but they had not made any direct comparison with the health benefits.
The ASA (Advertising Standards Authority), in its ruling, said the Quorn ad had not breached any rules on points two and three.
But on the first point – the claim that cod and tuna were endangered species – the ASA took issue with.
The ASA said Quorn had not provided enough evidence to substantiate the claim and that the conservation status of the species could be an important factor in their buying decisions.
The ASA ruled that Quorn had to amend its claim that "popular fish like cod and tuna are endangered by overfishing" to make it clear not all species of cod and tuna were endangered.
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