Doctors are warning that a little-known but increasingly common sexually transmitted disease is in danger of becoming a superbug, with sexual health clinics lacking the tools to diagnose it properly.

Mycoplasma genitalium (MG) has similar symptoms to chlamydia but is more resistant to treatment and can lead to pelvic inflammatory disease in women and, ultimately, infertility.

MG, first identified in the 1980s, often has no symptoms but in women it can cause a burning sensation when urinating and pain or bleeding during and after sex. In men symptoms include include watery discharge from the penis.

Around one to two per cent of men and women are thought to be infected with the disease, although rates in some STD clinics are as high as 38 per cent.

The British Association of Sexual Health and HIV (BASHH) has launched new guidelines for the treatment and diagnosis of the disease, which recommend a specific diagnostic test: a nucleic acid amplification test.