Half of people diagnosed with HIV are identified late and could have benefited from earlier treatment, according to a new report.
An estimated 91,500 people in the UK were living with the disease in 2010, with a quarter of those unaware they had it, Health Protection Agency (HPA) data showed. The figure is up on the 86,500 living with the condition in 2009.
Of the 6,660 people newly diagnosed with HIV in 2010, half came forward for testing after a time when treatment should ideally have started.
In 2010, more than 3,000 gay men were diagnosed with HIV - the highest ever annual figure. One in 20 gay men are now infected with HIV nationally, rising to one in 11 in London.
But heterosexual men remain the most likely group to be diagnosed late, at 63% compared with 39% of gay men and 58% of heterosexual women.
The data also showed that one in five people visiting a sexually-transmitted infection clinic in 2010 did not accept an HIV test.
The HPA is recommending that, in areas where prevalence of HIV is high, testing should be offered in places where it is not currently the norm. Testing should be offered to all people signing up with a GP and those admitted to hospital, but only with the patient's permission.
Dr Valerie Delpech, consultant epidemiologist and head of HIV surveillance at the HPA, said: "HIV is an infection which can nowadays be treated and those diagnosed promptly can expect to experience similar life expectancy as an individual without the infection.
"However, we are very concerned that a large number of people in the UK are unaware of their HIV status and are diagnosed late. We want to see increased access to HIV testing routinely offered in clinical settings such as new registrants at GPs and hospital general admissions, in areas of the country where rates of HIV infection are high."
Sir Nick Partridge, chief executive of the Terrence Higgins Trust, said: "HIV rates in the UK remain dangerously high and to bring them down we all have to take responsibility for our sexual health. We can't just rely on partners, or chance, to keep sex safe."