Kentucky Fried Chicken (KFC) is at the centre of a legal test case alleging cruelty to millions of chickens, reports the Evening Standard.

Animal welfare campaigners have accused the company of claiming high standards while endorsing cruel practices.

The case was lodged in California this week but could have implications for its farming practices in Britain and across the world. KFC insists its guiding principles are to treat animals with “care and respect”, claiming it imposes strict welfare rules on suppliers.

But People for the Ethical Treatment of Animals (PETA) has waged a six-month international boycott over KFC’s rearing standards, claiming it endorses a range of cruel regimes.

PETA claims that KFC outlets in the UK sell “Frankenchickens” – birds created to grow at unnatural speeds. Reaching an adult weight of 2kg in 42 days, the heart and lungs find it hard to cope and many suffer painful leg deformities.

Compassion in World Farming is currently pursuing a legal test case against the British government for allowing such a system to exist.

A spokesman for KFC in the UK told the Evening Standard that the company did not did not operate any chicken-production facilities itself, but sets standards for suppliers – which included a ban on antibiotic growth promoters.