Scottish Quality Salmon (SQS), which represents 65 per cent of Scotland's salmon farming industry, said the study was "seriously misleading".

The results of the study, published in the journal Science yesterday, ignored all of the health benefits of eating oily fish such as farmed salmon, as reported in "more than 5,000 scientific studies", SQS said.

Dr John Webster, SQS technical consultant, said the level of toxic and carcinogenic contaminants that the study revealed in farmed salmon still fell below the levels set by the US Food and Drug Administration (FDA).

Robert Rae, an Edinburgh fish merchant, said: “This report is absolute nonsense. It’s American, so you have to take it with a pinch of salt. Notice they say their own salmon is fine."

The joint US/Canadian study, the largest undertaken into pollutants in salmon, found chemicals linked to cancer and birth defects in fish from supermarkets and wholesalers.

It found that the amounts of 14 toxins, including PCBs and dioxins, were significantly higher in European and North American farm-raised salmon compared to fish caught in the wild.

The report also stated that the most contaminated fish came from farms in Scotland and the Faroe Islands. The scientists tracked the source of the pollutants to the fish meal fed to intensively farmed salmon.

Neil Spreckley, managing director of EWOS, the world's largest salmon feed company, said: "PCBs are in everything, the sea, the land and other foods. Even the Food Standards Agency has said the dioxins and PCBs found in the study were within the safety levels."

He added that he thought the report could discourage consumers to buy farmed fish, which would be "very damaging" to the industry.

Robin Harper, the leader of the Scottish Green Party, described the findings as "devastating" and has called for an immediate inquiry by the Scottish Executive. He said it was needed in order to protect the health of Scots and to secure the future of the Scottish farmed salmon industry.

"I want to know why it is that this polluted food is finding its way onto the dinner plates of Scots.

"I understand that salmon is regularly assessed by Executive agencies for some pollutants, but this report is a big sign that all is not well and the system of quality control is clearly failing," he said.

Scottish Tories meanwhile called for a measured response to the scientific study. Ted Brocklebank, the fisheries spokesman, said: "For the sake of the health of those who eat farmed salmon and for the livelihoods of the 6,500 people and their families who work in the industry many in the remotest areas of Scotland, we have to get the response right.

"If further changes, for example to feeding are needed to reduce risks and to reassure the public then they must be made. I call upon the minister to examine the facts carefully and to give a measured response", he said.

Meanwhile, Britain's supermarkets sought to reassure their shoppers that all was well with the farmed salmon they stocked on their shelves.

Sainsbury's said in a statement: "All Sainsbury's fresh salmon is produced by approved suppliers in clean waters in northern Scotland and Norway and is fully traceable to farms that comply with comprehensive welfare, environmental and safety requirements.

"Although we are aware of the concerns expressed in the Science magazine article, all of the results contained within the article are within EU safety limits.

"We are confident in the safety of all of our products and endorse the UK Food Standards Agency's recommendation that people should eat at least two portions of fish a week, one of which should be oily for health benefits."

Nick Nairn, a celebrity chef, urged Scots to continue eating Scottish salmon. He said: "I am not worried about it, these levels have been accepted by the Food Standards Agency as acceptable. The levels of dioxins have not changed, they haven’t found new dangerous levels, they have just said the existing levels are now dangerous.

"You have to put it into context: part of the reason there are so many dioxins is because of Western pollution in the first place. We don’t live in a perfect world, we have polluted our oceans and now we have to deal with the fall out," he said.

Colin Buchan, head chef at Amaryllis in Glasgow, said he hoped the report would not affect the salmon industry. He said: "I don’t think this [warning] will make much of an impact and salmon will not be coming off the menu."

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