The lifetime ban on gay men giving blood donations is to be lifted, but only for those who abstain for anal or oral sex for a year.
The change will be implemented by NHS Blood and Transplant in England and North Wales on Monday 7 November and by the Blood Services of Scotland and Wales on the same date.
The government's Advisory Committee on the Safety of Blood, Tissues and Organs (SaBTO) made the recommendations on Thursday.
According to research by the British Medical Journal, a year long deferral for blood donors is usual for other high risk groups.
Sir Nick Partridge, Chief Executive of Terrence Higgins Trust (THT), the largest HIV charity in the UK, said the regulation was based on the "heightened risk, as a group, of sexually acquired blood-borne viruses".
"Changing that depends on reducing gay men's risk of HIV and other STIs to the same level as the rest of the population, and re-emphasising the vital importance of safer sex as far too many gay men still become infected with HIV each year."
Lesbian, Gay and Bisexual charity, Stonewall described the move as a "step in the right direction".
But chief executive Ben Summerskill said the one year rule was "disproportionate".
"To retain a blanket ban on any man who has had sex with another man in the last year, even if he has only had oral sex, remains disproportionate on the basis of available evidence.
"Under the new rules, a gay man in a monogamous relationship who has only had oral sex will still automatically be unable to give blood but a heterosexual man who has had multiple partners and not worn a condom will not be questioned about his behaviour, or even then, excluded," he said.
But Dr Lorna Williamson, research director for NHS Blood and Transplant's Medical and Research said: "It is essential that our donor selection rules are based on good evidence to maintain their credibility with donors, and this change gives us an updated policy that is proportionate to the current risk."
Fears surrounding the spread of aids in the 1980s led to a lifetime ban on blood donation by any man who had engaged in either oral or anal sex with another man.
HIV has been on the increase since the 1980s and there have been improvements in blood screening techniques. Yet there is still a "window period" after HIV infection during which the virus is undetectable.
A survey of homosexual men by the organisers of the UK’s biggest gay pride parade suggested 95 per cent of gay men would be willing to donate blood.
Nearly half of all men with experience of male penetrative sex held that they would donate blood regardless of the rules because they believed blood screening to eliminate the risks, according to research by the British Medical Journal, also released on Thursday.