A new HIV test which takes only 20 minutes to deliver a result is now available on the NHS.

Previously, those wishing to take an HIV test had to wait a week for their results.

The new test, which uses a special absorbent toothbrush to collect saliva samples from the mouth, was found to be as effective as a blood test.

It has been introduced at Barts and the London NHS Trust in London, where doctors expect to carry out around 250 tests a month.

Merie Symonds, head of sexual health at the trust, said: “Approximately a third of people in the UK who are HIV positive are currently unaware of their condition.

“There are still very real problems due to people who are not testing until they have become unwell as a result of undiagnosed HIV infection. This means that treatment that is now widely available may not work as effectively.

“Making testing for HIV quicker and easier is a real step towards getting people to test sooner. As this test doesn’t require us to take blood or send samples to a laboratory, we can begin to look towards testing outside traditional clinical areas.

“We are already offering this test to service users in some of our outreach services run in non-healthcare settings.”

The test is currently being offered to all people from areas of high HIV prevalence and to men who have sex with men, in addition to those who are sexually active with either group.

Earlier this month, charity Unicef warned that Britain now has the highest number of new HIV infections in western Europe, with gay and bisexual men and black Africans most at risk.

In 2007, there were more than 7,700 new HIV diagnoses in the UK and the organisation has also said infection rates in young people are rising, with ten per cent of new infections occurring in those aged between 16 and 24.

The second highest figure for new infections was in France, with 4,075. Germany, which has ten million more people than Britain, had 2,752 new cases.

Four in ten of those diagnosed with the disease were men who have sex with men.