The charity says labelling of fresh fish at fish counters, takeaways and restaurants is "poor and, in many cases, non-existent" and as such is not keeping pace with public concern for the sustainability of food supplies.
MCS Fisheries Officer Sam Wilding said: "Labelling of seafood sold in the UK is lacking detail, and as such is not fit for purpose. This is leading to confusion amongst consumers who really want to make the best sustainable seafood choice. It is vital that consumers are given better information to act upon if we are to reduce the tragedy of overfishing."
Much confusion still surrounds cod which has stocks at various levels of abundance in different regions and the MCS advises the use of pouting, red or grey gurnard and pollack as sustainable alternatives.
Tom Aikens, who was forced to close his Chelsea fish restaurant Tom`s Place last week after complaints about the smell from neighbouring residents, has been sourcing sustainable seafood for three years in all his restaurants.
He serves gurnard and pollack as alternatives to cod which he said have "proved popular" with patrons.
"Both these species are excellent alternatives to cod and can be prepared in the same way," he added."
The MCS has created a website www.fishonline.org with advice about almost every fish on sale in the UK and has also produced the MCS Pocket Good Fish Guide which can be downloaded from the website or sent out free (upon receipt of SAE) by calling 01989 566017 or email firstname.lastname@example.org.
Tom Aikens forced to close restaurant