It might be one of the nation’s favourite meals. But is that actually cod on your plate?
The answer is apparently 'no' in some cases. In fact, you might have bought a type of catfish - the cobbler - that comes from south-east Asia.
Cheaper types of fish have been labelled incorrectly as more expensive cod, according to research led by a Salford University academic.
Dr Stefano Mariani, a marine biologist, also told MSN News that there was a potential risk to people who had food intolerances if fish was mislabelled.
He used DNA testing to check whether cod being sold in Ireland and the UK was actually cod.
The research has hit the headlines in the wake of the horsemeat scandal.
But the association representing fish and chip shops has insisted there isn't a problem with its industry.
How much cod has been mislabelled?
He tested samples from supermarkets, takeaways and fishmongers - and found 7.4% of cod in the UK was mislabelled compared to 28.4% in Ireland.
“We found that substitute species could be pollock, haddock, whiting and the cobbler," said the academic.
He added: “We found some products labelled as Pacific cod but they were found to be unarguably Atlantic cod.”
Dr Mariani said that could be a problem for consumers trying to be more environmentally friendly by buying fish less at risk from overfishing.
Pacific cod that has been illegally caught could also have been relabelled to put it back into the food chain, he suggested.
In terms of food safety, he added: “We don’t know until something bad happens because by and large it is safe.
“The only major short-term problem is if there is some financial wrong-doing, people selling cheaper species for more expensive ones.
“But if the label doesn’t quite tell the truth, some people have food intolerances. There could also be some health risks in that case, but it is difficult to assess how likely it is.”
To tackle the problem, Dr Mariani said: “Better legislation helps, but also following the legislation with enforcement.”
And it’s not just a problem in the UK, it seems.
Mislabelling in the US
Research by Oceana, an international organisation focused on ocean conservation, found that a third of 1,215 samples it tested from across the US were mislabelled.
For example, samples sold as snapper and tuna had the highest mislabeling rates (87% and 59%, respectively).
Just seven of the 120 samples of red snapper purchased nationwide were actually red snapper. The other 113 samples were another fish.
One of its scientists, Kimberly Warner, told the BBC that the problem of mislabelling mattered because of the deception of consumers, but also because it put overfished species at risk.
The BBC quoted Dr Bert Popping, director of scientific development at the Eurofins laboratory in Hamburg, as saying that tests are turning up types of fish that have never been in the food chain before.
What about fish and chips?
Andrew Crook, treasurer of the National Federation of Fish Friers, said: "Fish and chips have been working hard to make sure that our shops, our industry, tells the consumer what species they are consuming.
"But I know that other food establishments hide a lot of other things under the white fish label."
He added: "At the point of sale, it should be clear what species you are selling."