All birds on the infected premises, near Alcester in Warwickshire, will be culled.
The outbreak comes less than week after the United Kingdom declared a country-wide Avian Influenza Prevention Zone, ordering farms and bird keepers to toughen biosecurity measures.
The H5N1 strain had previously been confirmed at small backyard flock of chickens in north Wales, among captive birds in east Scotland and at a bird rescue centre in central England.
The virus has been spreading across Europe during the last few weeks with outbreaks in several countries including France, Germany, Italy, the Netherlands and Denmark.
Poland on Monday also reported several outbreaks of highly pathogenic H5N1 bird flu at poultry farms with flocks totalling nearly 650,000 birds, the World Organisation for Animal Health (OIE) said.
Five outbreaks, of which four at fattening turkey farms and one at a chicken broiler farm, were found in the eastern part of the country while another was discovered at a turkey and geese farm in the western part of the country, the OIE said, citing a report from Polish authorities.
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