An estimated 73,000 British adults are living with HIV, yet around a third of these (21,600) are unaware they are infected, figures suggest.
The latest sexual health report from the Health Protection Agency (HPA) highlights high levels of HIV transmission among gay men, as well as steady increases in all sexually transmitted infections (STIs).
Dr Valerie Delpech, head of HIV surveillance at the agency, revealed that since 2003, the number of annual HIV diagnoses has consistently increased.
The overall sexual health of young adults worsened in 2006, with one in ten screened by the National Chlamydia Screening Programme testing positive for the infection.
The director of the HPA's Centre for Infections, Professor Pete Borriello, said that overall STI diagnoses had increased by 2.4 per cent between 2005 and 2006.
'We need to reinforce the safe sex message for gay men, young adults and the broader community,' he said.
'The best way to protect yourself from contracting an STI including HIV is by practising safer sex by using a condom with all new and casual partners.'
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