The Soil Association, which promotes and certifies organic food producers, said it had given its full backing to organic aquaculture in the UK.
The move ends an eight year 'interim period', imposed on fish farmers by the Soil Association until production standards and controls in the supply chain had improved.
The breakthrough offers UK fish farms a chance to profit from Britain's fast-growing organic food market.
Sales of organic food in Britain rose 30 per cent last year to nearly £1.6bn, according to the Soil Association, largely led by consumer concerns over food safety and health.
Supermarkets were also instrumental in the rise by giving organic food more shelf space.
Fish farmers are now hopeful they can take advantage too. "Whilst it's more challenging to grow fish organically - and there are many more guidelines to adhere to - there's no doubt there's a good future for organic fish farming with more and more people looking to buy products which are free of chemicals," said Lewis Macleod, who runs organic fish firm Lewis Salmon in Scotland.
It is mostly small-scale producers like Macleod who will take advantage of organic markets for now, according to the Soil Association, which says 85 per cent of Scottish salmon farms are owned by Norwegian multinationals.
The Soil Association said it now wanted to further improve organic fish standards. Priorities include sustainable fish feeds, as well as moving away from potentially polluting veterinary treatments and farming multiple species of fish, sea-weed and crustaceans to minimise nutrient losses.
UK supermarket Waitrose, has signed a deal with the Soil Association to ensure that all fishmeal and oil used as feed on organic fish farms comes from waste from fisheries certified as 'sustainable'.
Other signatories in the deal are the sustainable seafood firm, Aquascot, and the Marine Stewardship Council.
One problem, however, is whether fish farms will be able supply enough fish for the market if more go organic.
The Soil Association says organic fish farms generally have half the fish of conventional farms. With sea stocks declining, fish farming is expected to become our principal source of fish in the next 20-30 years.
Peter Bridson, a Soil Association aquaculture specialist, said organic fish was a winner for consumers, producers and the environment.
"A key factor in choosing organic farmed-fish is that this premium product allows smaller-scale, locally-based producers to make a living whilst respecting the ecological constraints of the aquatic environment."