Chip shops and restaurants are selling ‘fake cod’ to unwitting customers by serving cheaper and lower-quality fish than the species advertised.

The Argus found three food premises in Sussex have been reprimanded for serving up substandard species of fish in the last three years – despite advertising the fish as cod on their menus.

All three restaurants were caught by West Sussex County Council Trading Standards teams.

However council chiefs are protecting the restaurants by refusing to reveal their identities.

They included a time in January this year where a restaurant in Shoreham dished up a fish pie with smoked salmon, cod and prawns to its customers – but used striped catfish and haddock instead of cod. The owners of the venue were given a warning letter.

An inspection at a Horsham restaurant in May last year found the fish in an ale battered cod and chips dish was haddock. The restaurant’s owners were given a caution.

Another occasion at a venue in Crawley found blue tilapia fish was being used as the main ingredient in a cod jalfrezi dish. The restaurant’s owners were given a warning letter.

West Sussex Trading Standards refused to identify the restaurants, citing legislation from the 2002 Enterprise Act.

A Trading Standards spokesman said: “There are some exceptions to this exemption. For example if the business agrees to the disclosure, it is already in the public domain, and also we can disclose to other enforcement agencies.

“It would also not be relevant if the businesses had been prosecuted and convicted as this would then be in the public arena.”

Despite being home to scores of fish and chip shops and seaside premises, East Sussex County Council and Brighton and Hove City Council said they had not found any food premises serving fake cod in the last three years.

A Brighton and Hove City Council spokeswoman said: “Brighton & Hove City Council Trading Standards Food Team reports no cases of fish inaccurately sold as cod in the city. Last year, the council took part in the Food Standards Agency sampling plan, submitting three cod samples for testing. All three samples were taken from businesses with historical complaints of substitution and all proved to be cod.

"During the same period, we looked into about half a dozen complaints from members of the public. The premises were inspected in these cases. Skin markings of fish on sale and purchasing invoices were examined. There were no substantiated complaints."