Nearly 100,000 people are now living with HIV in Britain, the Health Protection Agency revealed today.
Officials said a quarter of the record-high 96,000 people were unaware they were infected.
The agency said there were 6,280 people diagnosed with HIV in 2011.
The new 3,010 homosexual men diagnosed was also an all-time high.
Nearly half of new diagnoses were heterosexual men and women, around half of whom probably contract HIV in Britain, compared to only 27 per cent in 2002.
The agency's head of HIV surveillance Dr Valerie Delpech said promoting HIV testing and condom use is crucial to tackling the high rates of transmission, late diagnosis and undiagnosed HIV still seen in Britain.
She encouraged clinicians to take every opportunity to offer the test to those in higher risk groups and, in high prevalence areas, to all general medical admissions and new GP registrants.
Terrence Higgins Trust charity chief executive Sir Nick Partridge said: "Thirty years on from the start of the epidemic, public understanding of HIV has dropped to a worrying level.
"As a result, we are starting to see a significant increase in the number of heterosexuals acquiring the virus in the UK.
"It is important that everyone, no matter their age or background, understands that nobody is immune from infection."
He added that a simple HIV test - offered free at clinics and testing services all over the country - might add over 40 years to the life of someone with HIV, diagnosed in good time.
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