The World Health Organisation (WHO) has rejected calls from 150 leading scientists to move or postpone the Rio Olympics because of the ongoing Zika virus.
The group of experts signed an open letter to the WHO and International Olympic Committee (IOC) asking for the Games to be halted or held in another location "in the name of public health".
Professor Amir Attaran, one co-authors of the letter, said the Games risked becoming "the Olympics of brain damage" if they went ahead as planned this summer.
But the WHO told the BBC that suspending the Olympics or staging them elsewhere would "not significantly alter" the spread of the virus, which is linked to serious birth defects.
The letter signed by 152 global health experts states that the Zika virus has more serious medical consequences than previously known and that the emergency contains "many uncertainties".
Some 500,000 foreign tourists are expected to attend the Games, which would lead to the virus being spread across the globe to areas it may not have reached if it was not for the Olympics, the letter warned.
The experts, many of whom have worked with the WHO, also voiced concerns over the relationship between the UN's health agency and the IOC, which they said entered an official partnership in 2010.
Prof Attaran called the partnership "beyond the pale" and called into question the independence of the WHO.
"It is ignorant and arrogant for the WHO to march hand-in-hand with the IOC," he said. "How can it be ethical to increase the risk of spreading the virus? Just because a fire has begun doesn't mean you need to pour gasoline on it."
The WHO declared the Zika epidemic to be a global emergency in February and in its latest assessment this week, said it "does not see an overall decline in the outbreak".
Professor Attaran said he believed allowing the Olympics to go ahead in Rio would lead to the birth of more brain damaged children.
The majority of those infected with Zika will have no symptoms, but for others it can cause a mild illness with symptoms including a rash, fever and headache.
Serious complications that arise from infection are not common, but experts have said the virus can cause microcephaly, where babies are born with abnormally small heads due to the fact their brains have not developed properly.
Pregnant women have already been advised not to travel to Rio and the WHO have predicted the Zika risk in August would drop since it will be the south American winter and there should be fewer mosquitoes.
The experts' letter dismisses this claim because many visitors to Rio may return to countries with a hotter climate.
The IOC has previously said it sees no need to cancel, delay or move the Rio Games because it had been "advised by the experts that the situation will improve over the next three months".
WHO director-general Dr Margaret Chan said earlier this month that the UN health agency is increasingly worried about Zika, but stopped short of recommending the Olympics be moved or postponed.
In a statement, the WHO said: "Brazil is one of almost 60 countries and territories which to date report continuing transmission of Zika by mosquitoes.
"People continue to travel between these countries and territories for a variety of reasons. The best way to reduce risk of disease is to follow public health travel advice."
No Olympic Games have been moved because of health concerns, but in 2003 Fifa moved the Women's World Cup from China due to the respiratory virus Sars.
The opening ceremony of the Olympic Games is due to take place at Rio's Maracana Stadium on August 5.