The “cocktail” of infections to which birds are subjected creates a near-perfect breeding ground for a disease outbreak of pandemic potential, according to the report by the non-profit organisation Open Cages.

The authors of the report warn that a new bird flu virus with “high transmissibility” would make COVID-19 appear mild claiming that supermarkets are primarily responsible for this “cruel and dangerous” system, because to keep prices low, they reportedly buy chicken from farms with overcrowded conditions that mean disease can spread easily.

They also allegedly use breeds engineered to grow unnaturally rapidly, known as “frankenchickens”, that are “practically unable to ward off infection when it strikes” because their immune systems are so weak.

Nearly a billion broiler (meat) chickens a year are reared in the UK, making it the country’s most-farmed land creature.