Sustainability and catching methods have overtaken freshness as the key selling points for chilled fish products and paved the way for more previously frozen fish to hit supermarket chiller cabinets.

Hardly any of the UK multiples prioritised the fresh message any longer and many now happily sold fish that had previously been frozen, according to a £40,000 research project funded by the Norwegian white fish industry.

"You used to see labels on chilled fish saying the product had been air-freighted to maximise freshness, but now messages about handling, such as line-caught fish, and sustainability have become more important," said Finn-Arne Egeness, a scientist at the Nofima research institute who worked on the project.

"Of all the British supermarkets we looked at, only Morrisons makes it clear on its fresh fish counter that the fish has never been frozen."

As far as the other multiples were concerned, interest in never-frozen fish had waned over the past five years, Egeness added. This had been driven initially by a desire to secure a more regular supply of cod all year round.

"Fresh cod can be difficult to get hold of, especially in the summer time, so suppliers tried frozen product, which gives them much more control as it can be stored in warehouse and thawed when needed."

The UK is a key export market for Norwegian fresh cod, and greater acceptance of a once-frozen product on British shelves means Norwegian suppliers could soon face more competition from other countries, including Poland.