There is "huge concern" among British doctors that "super-gonorrhoea" is spreading across the country.
The highly drug-resistant strain of the sexually transmitted superbug is at risk of becoming untreatable if the only fully effective antibiotic remaining fails, experts say.
There have been efforts to track down the sexual partners of those infected with the disease, which can cause infertility.
However Public Health England is understood to have acknowledged that efforts to contain the spread have been of "limited success".
The alert comes after Chancellor George Osborne warned resistance to antibiotics will become "an even greater threat to mankind than cancer" without global action.
PHE said an increase in cases of super-gonorrhoea was a "further sign of the very real threat of antibiotic resistance to our ability to treat infections".
