The UK's Food Standards Agency has issued a warning to British poultry importers and retailers after chickens from Portugal were found to contain traces of a banned veterinary drug.

The FSA is advising importers and retailers against selling these products unless they can be shown to be free of nitrofuran antibiotics.

It is illegal to use nitrofurans in food producing animals in the European Union because of health concerns including a possible increased risk of cancer in humans through long-term consumption.

The health risk from eating an affected chicken is low because concerns relate to long-term exposure to these drugs.

The FSA said Portuguese chicken makes up a small proportion of poultry imports into the UK, a total of 178 tonnes last year.

Dr Andrew Wadge, Acting Head of Food Safety at the Food Standards Agency, said: 'This is a disturbing finding as it is unacceptable that any chickens should contain traces of nitrofurans, which have been banned in food within Europe since 1994.

'The food industry needs to check that if they are buying Portuguese chicken they are free of nitrofurans. Consumers need not be unduly alarmed about the health risks as imports of Portuguese chicken are very low and you would need to eat a lot of it over many years for there to be an effect.

'However, it is important that this issue is addressed by the Portuguese and European authorities as quickly as possible.'

The Portuguese authorities discovered the illegal use of nitrofurans after carrying out tests during routine sampling. Samples from all 43 farms tested proved positive.
 
The Portuguese Government is destroying poultry from all these farms and is testing the remaining Portuguese poultry farms as part of a detailed investigation.

It is not yet clear how the nitrofurans got into the chickens or how widespread the problem is.

The FSA has asked the European Commission to discuss this issue as a matter of urgency.