Gay men will be able to give blood when government restrictions are lifted later this year, the Department of Health said today.
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.
The recommendation has been accepted by the health ministers in England, Scotland and Wales, and the ban will be lifted on November 7.
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.
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.
The change means the criteria for men who have had sex with men will be in line with other groups who are deferred from giving blood for 12 months due to infection risks associated with sexual behaviours.
These include women who have slept with a man who has had sex with another man, people who have slept with prostitutes and those who have had sex with anyone who has injected themselves with drugs.
Current guidelines say people can never give blood if they have had syphilis, HTVL (Human T-lymphotropic virus), hepatitis B or C, and a lifetime ban is also in place for people who have ever worked as a prostitute or anyone who has injected themselves with drugs.
Today's announcement was welcomed by human rights campaigner Peter Tatchell, but he said it 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."
The activist 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."
Public Health Minister Anne Milton said: "Blood donations are a lifeline, and many of us would not have loved ones with us today if it was not for the selfless act of others.
"Our blood service is carefully managed to maintain a safe and sufficient supply of blood for transfusions.
"Appropriate checks based on robust science must be in place to maintain this safety record and the Committee's recommendation reflects this.
"It is important that people comply with all donor selection criteria, which are in place to protect the health of both donors and transfusion recipients."
The change will be implemented by both NHS Blood and Transplant (NHSBT) in England and North Wales and the Blood Services of Scotland and Wales.
The Scottish Government asked the Scottish National Blood Transfusion Service (SNBTS) to implement the changes from November 7.
Health Secretary Nicola Sturgeon said: "The UK Advisory Committee on the Safety of Blood, Tissue and Organs has looked in depth at all the latest scientific evidence in this area, including improvements to blood screening and changes to donation criteria overseas, and recommended these changes on the basis of that evidence.
"On that basis, I have accepted this expert advice in relation to blood donations in Scotland.
"These changes will bring the criteria for men who have sex with men into line with other groups who are deferred from blood donation for 12 months due to sexual behaviours while ensuring every possible step is taken to maintain the safety of our blood supply."
Keith Thompson, SNBTS national director, said: "The safety of the blood supply is paramount so that we can protect patients from the risk of acquiring an infection and we are pleased that this new donor selection criteria has been made possible by the most up-to-date scientific advances in screening and testing.
"Blood donation works on the principles of kindness and mutual trust, and in order for us to safely introduce this new rule we ask all potential and existing donors to adhere to the blood donor selection criteria by providing completely honest answers to all the questions, both for the protection of their own health and that of patients."
Nathan Sparling, LGBT officer of the National Union of Students Scotland, welcomed the decision but added: "We are disappointed that the Government has chosen not to publish research to support its decision to introduce a one-year deferral for men who sleep with men donating blood."
Carl Burnell, chief executive of gay men's health charity GMFA, said: "The removal of the ban to a one-year deferral is great news but it's going to leave some gay men frustrated that they still can't donate blood.
"However the one-year deferral is based on scientific evidence to ensure the safety of the blood supply in relation to Hepatitis B and HIV.
"Gay men can play their part in ensuring the UK has a safe supply of blood for everyone, including gay men, by adhering to the one-year deferral."
Meanwhile, the National Aids Trust called for the decision to be reviewed in future.
Chief executive Deborah Jack said: "This decision is now based on evidence and the safety of the blood supply will be maintained.
"However, we are adamant that this decision will need to be reviewed again in the future as science and the HIV epidemic evolves, and new evidence emerges."