The restrictions were put in place in the 1980s to prevent the risk of HIV contamination.
However, the latest medical evidence presented to a government panel argued the ban could no longer be justified.
Ministers in the three countries accepted the argument and said they would be relaxing the rules. Northern Ireland is expected to make a decision soon.
The move follows a report by the government’s Advisory Committee on the Safety of Blood, Tissues and Organs, which said the lifetime ban was no longer justifiable.
Canada and the United States still prohibit gay men from donating blood.
The bans were imposed in the 1980′s, amidst the early days of the HIV/AIDS crisis.