The advice, from the British Dietetic Association to its members, comes after recent government research revealed traces of dioxins and PCBs, which are believed to cause cancer and have "gender-bending" effects, in samples of fresh fish, as disclosed by the Independent on Sunday last week.
The highest levels were found in oily fish, a prime ingredient of the Mediterranean-style diet that successive governments have urged Britons to adopt to improve their health.
According to the BDA advice, the protective health benefits of eating at least some oily fish - such as mackerel, herring, sardines or salmon - each week outweigh the "clear ... potential problems of contamination of fish and fish oils with PCBs and dioxins".
Gaynor Bussell, BDA spokeswoman, told the Independent on Sunday that adults not at risk of heart problems are best advised to eat only one portion of oily fish a week. "Anyone taking more than that is exceeding the amount needed on health grounds," she said.
Asked if the advice meant that healthy people might be imperilling themselves by eating more, she replied: "I take it to mean that it is not a good idea to eat more than one portion a week unless you are at risk of coronary heart disease or have a history of heart problems."
The Department of Health insisted last week that it had no plans to update its advice to the public on diet despite mounting concerns over food safety - in particular the use of pesticides on fruit and vegetables, and of antibiotics as growth promoters in chickens. Its advice is limited to the nutritional content of the diet, not how the food is sourced or produced.Reuse content