A survey suggests that one in five people do not know that HIV can be passed on through unprotected gay sex.

The poll of 1,944 people, by the National AIDS Trust, also found that the same number did not realise that unsafe heterosexual sex could lead to transmission of the virus.

African and Caribbean people were least likely to know that unprotected gay sex was a route of transmission – 49 per cent compared with 20 per cent overall.

This is the fourth year that the charity has published the annual survey ’HIV: Public Knowledge and Attitudes’.

Researchers said it was particularly concerning that more people now wrongly believe that HIV can be caught through kissing (nine per cent) and spitting (ten per cent). These figures have doubled from 2007′s survey from four per cent and five per cent respectively.

Less than half of the public (45 per cent ) believe HIV can be passed from person to person by sharing needles or syringes. Only 30 per cent were able to correctly identify all the ways HIV can and cannot be passed on.

Sixty-seven per cent of people said they had sympathy for those with HIV and 74 per cent believed they should have the same level of support and respect as people with cancer.

Eleven per cent had no sympathy, rising to 30 per cent towards those infected with HIV through unprotected sex.

Almost half of people (47 per cent) thought that there are no effective ways of preventing a pregnant mother with HIV from passing HIV on to her baby.

Evidence shows that the right treatment gives an HIV-positive mother a 99 per cent chance of having a healthy baby.

Deborah Jack, the chief executive of National AIDS Trust, said: “It is certainly positive to see the majority of the public have supportive attitudes towards people with HIV, but there are still huge gaps in awareness of what it means to live with HIV in the UK today.

“It is extremely important that inroads are made in terms of educating the general public so we can eradicate the prejudice which still exists around HIV. In addition to improving knowledge of HIV, intensive work also needs to go into tackling the often deep-seated judgments and beliefs held about HIV and the people affected.

“The government made a concerted and effective effort to tackle this stigma in mental health, and now it is time for HIV to be addressed in the same way.”