The number of people living with HIV in the UK hit an estimated 86,500 in 2009, but more than a quarter - almost 22,500 - do not know they are infected.

Figures released by the Health Protection Agency show that 6,630 people were newly diagnosed with HIV in 2009 – 4,400 men and 2,230 women. Although this represents the fourth year-on-year decline in the number of new diagnoses, the agency says the evidence suggests that there has been no decline in the number of undiagnosed infections in the past decade.

The HPA’s report also found that over half of people newly diagnosed in 2009 – 3,450 – were diagnosed late. Valerie Delpech, head of HIV surveillance at the agency, said: “We’re very concerned that a large number of people in the UK are unaware of their HIV status and that half of all newly diagnosed people are diagnosed late, meaning they may not benefit from very effective treatments.

She added that the HPA would like to see increased access to HIV testing in areas where rates of infection are high. Pilot studies have shown that in these areas testing all adults registering at GPs or accessing certain hospital services can make an impact. Dr Delpech went on to say that evidence shows testing is "feasible to undertake and acceptable to patients".

She stated that hanks to the development of antiretrovirals "and universal access to world class health care through the NHS, HIV is a manageable illness for the vast majority of people in this country. We’re very pleased that eight out of 10 people in London newly-diagnosed with HIV are receiving immediate access to care but we need to ensure this is maintained and improved upon across the UK".