The number of reported cases of sexually transmitted diseases reached a record high in the US last year, figures show, as officials warned that stretched services meant people were slipping through the "public health safety net".

In its latest report, the Centres for Disease Control and Prevention said the sharp rise in syphilis was of particular concern.

"We have reached a decisive moment for the nation," Dr Jonathan Mermin, a director at the CDC, said.

"STD rates are rising, and many of the country's systems for preventing STDs have eroded. We must mobilise, rebuild and expand services - or the human and economic burden will continue to grow.”