Image caption A blood test can check for presence of the virus

As UK experts call for universal HIV testing in a bid to reduce infections, latest figures reveal a fifth offered the test at a sexual health clinic refused to have it.

The Health Protection Agency is concerned too few people know their HIV status, meaning many are treated too late and risk passing it on.

It says growing numbers of people are now catching the virus within the UK.

And cases diagnosed in men who have sex with men have reached an all time high.

The figures

The number of people living with HIV in the UK reached an estimated 91,500 in 2010, up from 86,500 the year before, with a quarter of those unaware of their infection.

Some 6,660 people were newly diagnosed with HIV in the UK last year.

People shouldn't be scared of HIV testing, but they should be scared of undiagnosed HIV Deborah Jack of the National AIDS Trust

Data revealed infections likely acquired within the UK almost doubled in the last decade from 1,950 in 2001 to 3,640 in 2010 and exceed those acquired abroad.

This rise is mostly due to infections acquired among men who have sex with men, who remain the group most at risk of HIV infection in the UK, says the HPA.

In 2010, over 3,000 gay men were diagnosed with HIV - the highest ever annual number. One in 20 gay men is now infected with HIV nationally and in London the figure is one in 11.

The report also revealed that in 2010, one in five people visiting a sexual health or genitourinary medicine (GUM) clinic did not accept an HIV test.

Over half of the people diagnosed in 2010 came forward for testing after the point at which treatment for their infection should ideally have begun, which greatly worsens their prognosis.

We encourage all people to take up the offer of an HIV test in whatever health care setting Dr Valerie Delpech of the HPA

The Health Protection Agency (HPA) wants universal testing for the infection in all new GP registrants and patients admitted to hospital in the areas of the country where there are high rates of HIV.

Testing call

Eight pilot projects have been carried out across England testing over 11,000 patients in hospitals and GP surgeries.

These successfully diagnosed 51 new cases of HIV, giving an overall detection rate of four in every thousand tests carried out. The HPA says this shows that universal testing would be feasible, cost-effective and acceptable.

But experience also shows not all those offered a test will agree to have one.

Dr Valerie Delpech, consultant epidemiologist and head of HIV surveillance at the HPA, says this has to change.

"People probably do not understand how easy it is to diagnose HIV and that with early treatment their chances of survival are near to normal.

"We are very concerned that a large number of people in the UK are unaware of their HIV status and are diagnosed late.

"We encourage all people to take up the offer of an HIV test in whatever health care setting."

The HPA envisages a future when no one leaves the GUM clinic without knowing their HIV status.

Just under 4% of England's population was tested for HIV in 2010. The bulk of these were people attending GUM clinics or women going for pregnancy check-ups.

Deborah Jack of the National AIDS Trust said it was time to eradicate people's fear about getting tested for HIV.

"People shouldn't be scared of HIV testing, but they should be scared of undiagnosed HIV.

"The advances in HIV treatment have been one of the biggest success stories in the 30 years since the virus first emerged, but too many people test too late and so fail to benefit from these drugs."

The Department of Health is due to publish a new Sexual Health Policy Framework in the Spring which will consider how to promote more HIV testing, especially in areas of high prevalence.