The charity warns there could be a threat to scallops

Marine officer Alistair Davison said: "The recent devastation to the scallop industry through forced fishery closures as a result of concern over shellfish poisoning may be linked to high nutrient levels from fish farms.

"The increase of nutrients in the sea may have caused these toxic blooms, which have become more frequent and cover larger areas than ever before."

WWF Scotland says it is particularly concerned that the Scottish Executive has been slow to pick up on concerns over nitrate pollution from salmon farming on the west coast of Scotland.

Mr Davidson added: "The sea on the west coast is much more diverse, sensitive and vulnerable to pollution than elsewhere in Scotland."

The group claims that fish farming on the west and north coasts of Scotland is responsible for releasing the same levels of phosphorous as the annual sewage of 9.4m people.

The warning is sounded in a report produced by the group called Out of Sight, Out of Mind.

Nutrient pollution is said to be to blame

The main sources of nutrients are agriculture, sewage, aquaculture and industry discharges, according to the report.

WWF says the government has failed to recognise the scale of nutrient pollution in the UK or to stick to its international commitments.

As a result, important marine areas are being jeopardised with their wildlife being endangered and lost.

The report outlines what it says are inconsistencies in government policy, treating freshwater and marine environments as separate by recognising the serious threat to freshwater habitats but not to the problem in estuaries and the marine environment.