Australian seafood importers are allegedly fooling traders, caterers and the public by "short-weighting" their goods; using additives and water to increase the weight of fish.

The accusation came from the Seafood Importers Association of Australasia, which called for the development of uniform laws to counter offenders.

Association vice-chairman Elaine Burn told The Age that the practice is almost an accepted part of the Australian seafood industry and it is so widespread that honest companies are loosing market share.

Association chairman Harry Peters added: "Instead of a kilo of prawns you might get 900 grams of prawns and 100 grams of water."

Most likely candidates for short-weighting are the products that easily absorb water, such as prawns, fish fillets, octopus, scallops and squid.