The practice of mislabelling fish appears to have been eradicated in Irish supermarkets thanks to widespread media coverage of the fishy business - but almost half of all takeaways are still codding customers, a new study has revealed.

University research published four years ago found that 28 per cent of all the fish sold as cod in Irish supermarkets and takeaways was actually cheaper species, including pollack and whiting. A separate study by the Food Safety of Ireland (FSAI) also found mislabelling was rife.

In the vast majority of cases, the mislabelled cod products were smoked, breaded or battered which allowed retailers and takeaways to effectively conceal the appearance, smell and taste of the fish fillets.

Once the story broke, the co-author of the report, Prof Stefano Mariani of the University of Salford and colleagues from UCD and the University of British Colombia tracked the impact of the media scrutiny and then revisited the same shops to genetically test the products which were labelled as cod.

The team published the results of their study in the journal Conservation Letters today and it shows that while the practice of mislabelling was completely wiped out in the surveyed supermarkets, the takeaway industry was still floundering - and mislabelling was still rife.

All told, 41.7 per cent of fish tested in fast food outlets was mislabelled as cod despite the fact that the practice had been exposed and had received widespread coverage.

“The timeline of events suggests that the negative media coverage generated by the first cod mislabelling study put the large supermarkets under intense scrutiny, which acted as a positive catalyst for change,” Prof Mariani said.

He suggested that supermarket chains had acted quickly because they “constantly compete to attract and maintain a faithful custom, and their size and financial power may allow them to exert greater control over the supply chain.”

However, the fish fraud is still widespread across the takeaway sector, “probably due to the less systematic custom and the convenient nature of the food”, Prof Mariani said and he called on the authorities to beef up its effective enforcement “in order to eradicate illegal practices in the sector”.