Gay men will be able to give blood from today as government restrictions are officially lifted, the Department of Health said.
A lifetime ban on blood donation by men who had had sex with another man was put in place in the UK in the 1980s as a response to the spread of Aids and HIV.
But following a review by the Advisory Committee on the Safety of Blood, Tissues and Organs (Sabto), men who have not had homosexual sex within a year will be able to donate if they meet certain other criteria.
Men who have had anal or oral sex with another man in the past 12 months, with or without a condom, will still not be eligible to donate blood, the DoH said.
They said this was to reduce the risk of infections being missed by testing and then being passed on to a patient.
Sabto's advisory panel, comprising leading experts and patient groups, carried out its review based on the latest available evidence and found it could no longer support the permanent exclusion of men who have had sex with men.
They considered the risk of infection being transmitted in blood, attitudes of potential donors in complying with the selection criteria and improvements in testing of donated blood.
Dr Lorna Williamson, NHS Blood and Transplant's medical and research director, said: "Our priority as a blood service is to provide a safe and sufficient supply of blood for patients.
"This change gives us an opportunity to broaden our donor acceptance on the basis of the latest scientific evidence.
"The Sabto review concluded that the safety of the blood supply would not be affected by the change and we would like to reassure patients receiving transfusions that the blood supply is as safe as it reasonably can be and amongst the safest in the world.
"There has been no documented transmission of a blood-borne virus in the UK since 2005, with no HIV transmission since 2002."
The change has been welcomed by the sexual health charity Terrence Higgins Trust.
Chief executive Sir Nick Partridge said: "We welcome this change, which is based on strong new evidence that all the experts are agreed on.
"These regulations will ensure the safety of blood supply for all of us while also being fair and equal in their application."
When the announcement was first made human rights campaigner Peter Tatchell argued the new rules fell short of lifting the ban on gay men who always use condoms.
He said: "Although the new policy is a big improvement on the existing discriminatory rules, a 12-month ban is still excessive and unjustified."
Mr Tatchell, who launched the first campaign against the lifetime ban on gay and bisexual blood donors in 1991, added: "Most gay and bisexual men do not have HIV and will never have HIV. If they always have safe sex with a condom, have only one partner and test HIV negative, their blood is safe to donate.
"They can and should be allowed to help save lives by becoming donors."
The move will be implemented in England, Scotland and Wales.