Tests were carried out on farmed salmon

The results confirm an earlier study carried out by Greenpeace that revealed levels of radioactivity were present in some Scottish farmed salmon sold in supermarkets.

The environmental campaign group found very low levels Technetium-99 (Tc-99) in fresh and smoked salmon bought from Sainsbury's, Tesco, Asda, Safeway, Waitrose, and Marks & Spencer.

The Food Standards Agency (FSA) conducted its own investigation into the possible contamination of fish.

The FSA's tests were conducted in conjunction with the Scottish Environmental Protection Agency (Sepa) and involved 14 fish farms in waters off Scotland and one in Northern Ireland.

The findings, which have yet to be published, detected traces of Tc-99 in fish at the Irish farm and four of the Scottish farms.

It is clearly not acceptable that something that could be avoided has ended up in the human food chain in this way Dr John Bell Food Standards Agency

FSA's chief executive, Dr Jon Bell, said it was unacceptable the chemical had ended up in the human food chain.

But he stressed there was no risk to consumers and revealed that a person would need to eat more than 91 tonnes of fish with these levels of Tc-99 every year to reach the EU dose limit.

"The vast majority of the samples did not pick up anything. In those that did, the levels were very low and below a cause for human health," he said.

"It is clearly not acceptable that something that could be avoided has ended up in the human food chain in this way."

Greenpeace said it was unacceptable for any level of radiation to be present in food.

A temporary ban on Tc-99 emissions has been imposed

Jean McSorley, nuclear campaign coordinator, said: "Technetium from nuclear reprocessing shouldn't be in fish bought by consumers.

"The fact that we have had our results confirmed is good but the real problem is how do you stop the discharges.

"There is no immediate harm to health. However, we know from other instances that radioactive waste may accumulate in sea food."

However Brian Simpson, chief executive of Scottish Quality Salmon, said that the salmon was perfectly safe.

He added: "Scottish salmon is entirely healthy and, as the FSA says, a person would have to eat more than 91 tonnes of fish to reach the EU dose limit."

Last month the UK Government asked British Nuclear Fuels to impose a nine-month ban on emissions of low level Technetium from Sellafield.

The Irish Government has put pressure on Britain to close the Cumbrian plant because of fears of the risk of radioactive pollution spreading across the Irish Sea.

Norway has also voiced concern because it has one of the world's largest salmon farming industries.