People are more ignorant of how HIV is transmitted than they were five years ago, a poll says.
Safe sex can prevent HIV transmission
Despite rising infection levels in the UK, 12% fewer people know the virus can be passed on through unprotected sex, the survey of 2,048 people revealed.
And the National Aids Trust study found some people still believed it could be passed on through kissing, spitting or sharing toilet seats.
Campaigners said the level of ignorance was worrying.
One in eight people would ask a new partner to take a HIV or sexually-transmitted infections test before stopping using condoms.
The poll found 79% knew HIV could be passed on through sex between a man and a woman without a condom - down from 91% in 2000. In London, where HIV rates are highest, only 70% of people were aware.
It also found that fewer than half would always use a condom with a new partner.
The poll also showed a drop in those who knew that HIV could be passed on by sharing infected drugs needles.
In 2005, 73% of people said they were aware of that fact, compared to 88% in 2000.
Some 7% though HIV could be passed on through spitting, 4% via kissing and 2% from toilet seats.
And 8% said they had no knowledge at all of how HIV was transmitted - up from 6% in 2000.
In London, where HIV rates are the highest, knowledge of HIV transmission was lower than anywhere else in the country.
NAT chief executive Deborah Jack: "We were very shocked to discover that while HIV is increasing in the UK, people know less about the risks of HIV transmission than they did five years ago and continue to practice unsafe sex.
"These results are a wake up call not only because people are putting themselves at risk, but also because ignorance about HIV is likely to encourage prejudice and discrimination."
And Lisa Power, head of policy at the Terrence Higgins Trust, added: "This is worrying, but sadly it is line with the trends of the last few years.
"We need more campaigns, people are becoming complacent."