A four-fold increase in syphilis infections has been blamed on people using social networking websites to meet for casual sex.

A public health expert made the link between the two today, saying that such websites were making it easier for people to meet and spread the disease, which disproportionately affects gay and bisexual men men.

Professor Peter Kelly, a director of health for NHS Tees, said that he was seeing rising levels of syphilis in his area.

He described it as a “devastating disease” and said that casual unprotected sex was the biggest cause of infection.

Prof Kelly said: “Unprotected sex, especially with casual partners, is the biggest risk for syphilis.

“Social networking sites are making it easier for people to meet up for casual sex.

“It is important that people avoid high-risk sexual behaviours and practise safe sex to protect themselves from sexually-transmitted infections.”

Syphilis can lead to serious illness and even death if left untreated. The discovery of penicillin in the early 20th century saw infection rates drop dramatically but they have been rising again since 2000.

Gay men are the most affected group and in 2005, 60 per cent of US cases were found in this group, compared to just seven per cent in 2000.

Simon Johnson, product manager for gay dating website Gaydar.co.uk, accused Prof Kelly of being “flippant” and said there were other causes for sexually transmitted diseases.

He said: “We find it questionable to place the blame solely on dating and social networking sites, it is clear that inadequate sex education at schools and the lack of consistent public health campaigns should be scrutinised before making flippant remarks.

“Gaydar.co.uk is proud to offer a wide range of services for members including one to one online counselling and group sessions to ask questions and get further information about sexually transmitted diseases. All provided by sexual health charities.

“We welcome Peter Kelly to get in touch with us to discuss his findings so that clear sexual health strategies can be developed for all communities.”