The world’s largest animal drugs company has been accused of double standards and of fueling the development of ‘superbugs’ by selling antibiotics to farmers in India for purposes now banned in Europe and the United States.

Zoetis, a former subsidiary of the drugs giant Pfizer, is supplying farmers in India with antibiotics to help them artificially fatten up livestock including chickens.

The World Health Organization (WHO) has called for the practice to be banned worldwide because it increases the prevalence of drug-resistant bacteria that can infect humans and cause deadly and untreatable infections.

The American company stopped advertising antibiotics as growth promoters to American farmers nearly two years ago and publicly supported new US laws banning the use of antibiotics to fatten livestock as part of its “continued commitment to antibiotic stewardship”.

However, Zoetis is continuing to sell antibiotics directly to Indian farmers with claims on the company’s Indian website that it will make animals grow bigger and faster. It is able to do so because the practice - although frowned on by the Indian authorities - is not illegal in India.

Dr Abdul Ghafur, a professor in infectious diseases who brought together medical societies and the Indian government in 2012 to create a plan to tackle antibiotic resistance, known as the Chennai Declaration, said Zoetis is using “double standards”.