The MRSA superbug has been found in British pork sold at Asda and Sainbury's, according to an investigation of dozens of supermarket products.
Tests on a sample of 97 pork products made in the UK revealed that three were infected with a strain of the superbug, which can cause severe health problems, the Guardian reported.
Two samples of minced pork from Asda and one from Sainsbury's were found to be contaminated.
The investigation by the newspaper and the Bureau of Investigative Journalism also found that a loophole in regulations means live pigs infected with MRSA CC398 can be imported from countries such as Denmark, where the superbug is widespread.
MRSA kills about 300 people in hospitals in England and Wales every year, and is known to have caused at least six deaths in Denmark.
Professor Tim Lang, of the Centre for Food Policy at London's City University, told the Guardian: "If we don’t have tight infection control and we don’t try to control the movement of live animals, infection can spread.
"The British are up in arms about the movement of people, but the EU also has a large movement of animals. We need biosecurity, we need to tighten up this livestock movement. You may get cheap meat, but in the long term it’s going to add to your public health problems."
A spokesperson for Asda said: "Our customers can be assured that we are working closely with industry groups and farmers to make sure that antibiotics are used responsibly in farm animals."
Meanwhile, a Sainsbury's spokesperson told ITV News that MRSA CC398 was “very uncommon” in British pork and that it worked with farmers “to ensure antibiotics are used responsibly".
"Through basic kitchen hygiene and thoroughly cooking meat, any food safety issue is removed," the spokesperson added.
Last month, a study commissioned by campaign group Save Our Antibiotics found that a quarter of chicken samples from Tesco, Sainsbury's, Asda, Aldi, Waitrose, the Co-op and Morrisons contained antibiotic-resistant E.coli.