AIDS patients who take effective retroviral drugs do not pass on the virus even through unprotected sex, Switzerland's state commission on the disease claimed on Wednesday.
Couples were one partner is HIV positive do not need to use a condom to prevent transmitting the disease, as long as retroviral therapy is followed regularly and has suppressed the virus in the blood for at least six months, the Federal AIDS Commission said in a report.
The patient must also be free of any other sexually-transmitted disease.
"These findings come from four different studies," said Bernard Hirschel, co-author of the report and an HIV/AIDS specialist at Geneva's University Hospital.
The claim sparked concern against AIDS charities who noted that the scientific research is focused on heterosexual couples and vaginal rather than anal sex.
One of the research studies was carried out in Spain from 1990 to 2003 on 393 heterosexual couples where one person was HIV positive.
The results showed that none of the HIV negative partners was infected by a patient taking retrovirals, according to a paper published in the Swiss Bulletin of Medicine.
Another study in Brazil found that out of 93 couples where 43 were HIV positive, only six people were infected and this was due to their partners not following their treatment regime.
Two other studies, one in Uganda and one on pregnant women, arrived at the same conclusions, Hirschel said.
However other health authorities and AIDS charities reacted with scepticism and alarm to the news.
"The real thing missing (from the Swiss advice) is about anal sex and getting a new sexually transmitted infection," said Roger Peabody of the London-based Terrence Higgins Trust AIDS charity.
"We don't feel the scientific evidence is conclusive and there are some key issues that are not covered in this advice," he added.
But Hirschel was adamant that publishing the results of the findings was in the best interests of the public.
"I know that these conclusions can provoke certain fears, but I think such credible information which relies on proven and certain facts should be made known," he said.
French AIDS charity Act Up said that only a small number of HIV patients would be affected by the findings, and that 40 percent of retroviral patients still carry the virus residually despite following their treatment to the letter.
France's National AIDS Council warned that the findings were not robust enough to extrapolate wider conclusions from the individual cases cited.