Families may be eating "critically endangered" shark when visiting their local fish and chip shop, warns a new study.
Endangered species of hammerhead and dogfish are among shark species being sold as food in Britain, reveals the research.
But most customers are unaware they could be biting into a species of fish battling extinction when they buy it at their local chip shop, fishmongers or Asian restaurants.
The University of Exeter study found that a staggering 90 per cent of shark sold at fish and chip shops in Britain was the globally threatened spiny dogfish, which is subject to international trading restrictions.
Meanwhile the scalloped endangered hammerhead shark was discovered in 40 per cent of shark fins sold in Asian restaurants and supermarkets.
But ambiguous and misleading labelling on menus means most people are completely unaware that they're eating shark, which could have been illegally imported.
Of the 78 battered and fried samples from fish and chip shops 90% were found to be spiny dogfish shark, a critically endangered species in the North Atlantic.
The researchers sampled more than 150 different shark products from fishmongers and chip shops in the south of England between February 2016 and November 2017, including London, Hampshire, Devon and Somerset.
For the first time in Europe, shark fins from a nationwide Asian food wholesaler destined for restaurants and supermarkets were also analysed using mini bar codes.
Dried and processed shark fins sold in Asian restaurants and supermarkets were also sampled, 38 per cent of which were the endangered scalloped hammerhead shark.
Meanwhile 25 per cent of samples were shortfin mako and 13 per cent smalleye hammerheads - also threatened species.
Catherine Hobbs of Exeter University, said: "It's almost impossible for consumers to know what they are buying.
"People might think they're getting a sustainably sourced product when they're actually buying a threatened species.
"There are also health issues. Knowing what species you are buying could be important in terms of allergies, toxins, mercury content and the growing concern over microplastics in the marine food chain."
She added: "Our findings demonstrate the need for more informative and accurate seafood labelling."
'Damaging trade in endangered shark species'
The majority of chip shop samples were sold under generic names such as huss, rock salmon and rock eel.
Researchers urged retailers to stop using misleading "umbrella terms" so customers know exactly what they're putting in their mouths.
Doctor Andrew Griffiths, also of Exeter University, added: "Scalloped hammerhead can be imported under strict conditions, but the wholesaler had no idea what species the fin belonged to.
"The discovery of endangered hammerhead sharks highlights how widespread the sale of declining species really is - even reaching Europe and the UK.
"Separate investigations focusing on Asia have commonly identified scalloped hammerhead in fin processing."
He added that the alarming findings, published in the journal Scientific Reports, "highlight the global nature of the damaging trade in endangered shark species, in which Europe and the UK have a continuing role."