Supermarkets are facing calls to reveal the levels of antibiotics in their imported pork after superbugs were found in the meat on sale abroad – from firms that may also supply UK stores.

Pork on supermarket shelves in Brazil, Spain and Thailand was found to contain superbugs resistant to some of the antibiotics critical in human medicine.

Britain imports nearly two-thirds (60 per cent) of its pork products – about 700,000 tonnes a year – and investigators believe it is likely that antibiotic-resistant superbugs will have infected some of the meat sold in the UK.

British supermarkets say they have already cut antibiotics in their supplies to avoid unnecessary use and that the risk to humans is low.

But it is feared Brexit will further increase the chances of pork carrying superbugs coming into the UK, as imports of lower-welfare meat may rise and British farmers lower their standards to compete on cost.

The World Health Organization (WHO) has warned that antibiotic resistance is a serious threat to human health that risks making everyday surgery and infections life-threatening.

The widespread use of the drugs in farm animals has been a large factor in the rise of antimicrobial resistance.

Superbugs in the food chain can cause pneumonia, fever, skin and urinary tract infections and, in extreme cases, death.

Experts from charity World Animal Protection tested pork sold in Australia, Brazil, Spain and Thailand, and found in three of the countries it was infected.

This shockingly highlights how overuse of antibiotics is a Band Aid solution to prevent cramped and stressed animals from getting sick World Animal Protection

Spain’s large pig meat exports industry is booming, thanks to a rise in demand from China, which has led to a massive increase in factory-farmed pigs, where welfare is often given a low priority.

Antibiotics are routinely used to fend off infections in animals kept crammed together in factory farms, “propping up” cruel systems and contributing to the superbug crisis, say critics.

The charity is calling on UK supermarkets to be more transparent about antibiotics in their supply chains following the test results.

Only Asda, the Co-op, Waitrose and Marks & Spencer reveal the amounts of antibiotics used in their meat products, and WAP wants the other stores to follow suit.

Pigs in an overcrowded shed in the EU (World Animal Protection)

“The results shockingly highlight how the overuse of antibiotics in factory farming has become a Band Aid solution to prevent cramped and stressed animals from getting sick, while also contributing to the superbug crisis,” a spokesman said.

“British supermarkets need to ensure high animal-welfare standards regardless of where pigs are raised, and should regularly publish data on antibiotic use in their supply chains to show they are meeting targets to reduce antibiotic use.”

He said progress had been made on reducing antibiotics in UK farming but the test results provided a snapshot of practices in different parts of the world.

Conditions in factory farms worldwide that require regular dosing of antibiotics include piglets being taken from their mothers when very young; pigs tails being cut and teeth clipped; male piglets being castrated and squalid sheds with floors coated in animal waste.

Jacqueline Mills, of WAP, said: “There is a better way. Higher-welfare systems allow for responsible antibiotic use, as has been proven in Sweden.

“We need to see an end to close confinement and barren environments, so pigs can live in social groups in comfortable environments with opportunities to express natural behaviour.

“Supermarkets should be setting the bar far higher to ensure the animals in their supply chains are less stressed, and antibiotics are used responsibly in farming.”

Helen Browning, Soil Association chief executive, said: “High levels of antibiotic use in pig farming is symptomatic of intensive farming systems that not only result in animal suffering but also pose huge threats to human health by contributing to antibiotic resistance.”

Sainsbury’s said it no longer used critically important antibiotics as a first-choice treatment in the pig and poultry industries, adding: “There are challenges to collecting robust and representative datasets for all species due to the different structures and challenges faced by each sector. We are continually working with our suppliers to improve the quality and quantity of data available.”

Sourcing of non-UK products always meets legal requirements British Retail Consortium

A spokesman for the British Retail Consortium (BRC) said: “Sourcing of non-UK products always meets legal requirements with many choosing to meet additional standards of best practice.

“The UK and EU risk assessments on the transmission of antimicrobial-resistant bacteria through food conclude that the risk to human health remains low.

“Retailers are working closely with their farmers and suppliers to ensure antibiotics are used responsibly in their supply chain, which means an appropriate balance between animal welfare and only using medicines when they are necessary as part of good husbandry.”

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Lidl UK said its animal-welfare policy banned routine usage of antibiotics and its suppliers were required to monitor usage through adherence to the Red Tractor scheme’s antibiotic use standards. A spokesman said: “We are committed to meeting sector targets and fully support the disclosure of antibiotic usage.

“However, we believe it is important to support suppliers through the development of a centralised, industry-wide approach. We work closely with RUMA (Responsible Use of Medicines in Agriculture Alliance) and industry groups, including the NFU, BRC, National Pig Association and Compassion in World Farming.”