The number of sexually transmitted infections (STIs) diagnosed in the UK continued to rise in 2005, with syphilis showing a 23 percent increase, the Health Protection Agency said on Tuesday.

Cases of the most common STI, chlamydia, increased 5 percent, but gonorrhoea fell 13 percent, the second successive annual fall.

Professor Peter Borriello, director of the HPA’s Centre for Infections, said that while the data on gonorrhoea were welcome, the overall figures were not good news.

“It is disappointing to see that there was a further rise in new diagnoses of STIs in 2005,” he said in a statement.

“Today’s figures serve as a reminder for people to take responsibility for their own sexual health and that of their partners, and to use a condom with new and casual partners.”

There was a significant increase in the number of new syphilis diagnoses, which rose by 23 percent from 2,278 in 2004 to 2,807 in 2005.

The HPA said new syphilis cases were particularly marked among women, where the increase was almost two and a half times higher than among men.

Chlamydia was the most commonly diagnosed STI, with 109,832 new cases last year, a 5 percent increase on 2004.

The HPA said the highest rates of infection and highest increases in diagnoses were seen in the 16 to 24 age group for both sexes.

Nick Partridge, chief executive of the Terrence Higgins Trust sexual health charity, said the figures showed it was vital to ensure access to treatment for STIs was quick and easy.

“We must keep pushing home the safer sex message,” he said. “It’s more important than ever.”