About 73,000 people in Britain are living with HIV, with a "continuing epidemic" among gay men, as the number of sexually transmitted diseases among the young continues to rise, a report found.

The Health Protection Agency's survey on the UK's sexual health said the number of new diagnosed STIs (sexually transmitted infections) had risen from 368,341 in 2005 to 376,508 last year, with people under 25 involved in many cases.

The report said that two-thirds of those diagnosed with genital chlamydia, 55 percent of those with genital warts and 48 percent of gonorrhoea infections had been young adults.

"Sexual health of young adults has worsened in 2006 with increases in sexually transmitted herpes and warts viruses," said Dr Valerie Delpech, head of HIV surveillance at the HPA. "One in 10 young adults screened through the National Chlamydia Screening Programme in 2006 tested positive for the infection."

The HPA's greatest concern was the growth in HIV cases. Figures showed 7,093 people had so far been diagnosed with the disease in 2006, a number expected to rise to around 7,800 when they had received all data. "We are still seeing high levels of HIV transmission in gay men in whom we anticipate that there will have been just over 2,700 new diagnoses of HIV infection in 2006," Delpech said. The HPA now estimates that about 73,000 in the country now have HIV, with about a third (21,600) unaware of their HIV status.

Professor Pete Borriello, director of the HPA's Centre for Infections, said control of HIV and STIs was a major challenge and that gay men should have regular HIV tests. "We need to reinforce the safe sex message for gay men, young adults and broader community," Borriello said.