Twelve people have been treated for infections linked to virulent strains of salmonella and E.coli carrying a deadly resistance gene.
At the same time, bugs carrying the gene have been found on three pig farms in the UK and chicken meat imported from Europe.
Just last month, scientists sounded the alarm over the dangers of global epidemics caused by infections that doctors would not be able to treat.
The warning followed the discovery of a superbug version of E.coli on pig farms in China.
It contained the MCR-1 resistance gene that disables the last-line antibiotic colistin, which would normally be used to treat humans after all other drugs have failed.
Three involved types of E.coli infecting two hospital patients. Two involved types of salmonella found on a single sample of chicken imported from the EU.
The fact that these bugs contained the MCR-1 gene means they are resistant to the antibiotic colistin, which is primarily used in the UK as a treatment of last resort for infections.
While the 12 British patients could not be treated with colistin, they survived after doctors found other drugs that worked.
At the same time as PHE was carrying out its tests, the Veterinary Medicines Directorate re-tested samples taken from pigs that have fallen sick on farms in the last two years.
Its experts found that E.coli taken from pigs on three different farms carried the resistance gene.
Britain’s chief medical officer, Professor Dame Sally Davies, has linked the use of antibiotics on farm animals to treat or prevent infections as being instrumental in the rise of superbugs.
She has called on ministers and the farming industry to radically reduce the use of such drugs, which are used particularly on intensive factory farms.
Dame Sally has painted an alarming scenario where even minor infections picked up during routine surgery could become untreatable with severe health consequences.
Speaking last year, she said: ‘Antimicrobial resistance poses a catastrophic threat.
‘If we don’t act now, any one of us could go into hospital in 20 years for minor surgery and die because of an ordinary infection that can’t be treated by antibiotics. And routine operations like hip replacements or organ transplants could be deadly because of the risk of infection.’
The fact that the superbug is in Britain was revealed by the Alliance to Save Our Antibiotics.
It claims the fact that colistin is frequently used for mass medication of farm animals has been instrumental in salmonella and E.coli developing a resistance.
The group has established that 837kg of colistin were sold for use in British farm animals in 2014, whereas just 300kg are used per year in human medicine.
Scientific advisor to the Alliance, C