Portugal has banned the sale of all chicken, turkey and quail meat due to the suspicion that a banned antibiotic that can increase the risk of cancer in humans has been used.

"While there is no evidence to suggest that the frozen bird meat which is currently being sold contains nitrofuran, recent developments advise caution in order to reinforce food safety and consumer confidence," the agriculture ministry said in a statement carried by the Lusa news agency.

The minister added that food safety inspections would continue to be carried out to ensure that no food-related consumer outlets were carrying frozen Portuguese poultry processed before the agreed date of 14 March.

The agriculture ministry has already announced that it has detected traces of the banned substance in samples from no less than 43 Portuguese farms. The farms were consequently shut and some 1.2 million animals are still under quarantine.

The results have so far proved positive for three of the farms and all the birds there have been destroyed, the ministry confirmed.

The exportation of poultry and fowl in Portugal is very small, accounting for just 1 per cent of the national market. Most exports end up in Spain and Angola, a former Portuguese colony.

Britain's Food Standards Agency has already issued a warning to importers and retailers in the UK about the danger of contaminated bird meat from Portugal, but also reiterated that the threat was very small as imports are minimal.