Campaigners have said they will seek a judicial review of NHS England’s decision not to commission a preventative HIV treatment.
The National Aids Trust (NAT) said the treatment called Prep can reduce the risk of HIV infection by more than 90%.
NHS England said it had repeatedly looked at the issue and will not fund it, although the NAT says the drug is “potentially revolutionary”.
The responsibility lies with local authorities, according to the NHS.
The NAT says it will take NHS England to court unless changes its mind.
Prep (pre-exposure prophylaxis) is a daily pill that can considerably lower a person’s chances of catching HIV.
If taken correctly, it is almost entirely effective in preventing HIV.
NHS England has promised £2m in funding to treat about 500 people with Prep over the next two years.
But after considering representations from stakeholders, it concluded that it was not the body responsible for offering the drug.
According to NHS England, local authorities are the “responsible commissioner” for HIV prevention services.
In a letter published in the British Medical Journal, NAT chief executive Deborah Gold said: “Faced with this impasse, NAT has no choice but to take the matter before a court for judicial review.”