The Government is expected to be told to make it considerably easier for gay men to donate blood in a dramatic winding down of the ban implemented amid the 1980s Aids epidemic.

An advisory committee is understood to have decided that the current deferral period, in which men cannot give blood within 12 months of having sex with another man, should be reduced to three months.

The change is in line with improved testing measures, which can establish whether someone has a blood infection, such as HIV, hepatitis B, hepatitis C or syphilis, inside three months.

Gay rights activists, who want to get rid of the blanket deferral period entirely, have hailed the potential shift in policy as a major step towards a fair and equal system.

Ethan Spibey, who founded Freedom to Donate after being turned away when trying to give blood as a thank-you to the donor who saved his grandfather’s life, and who was an adviser on the decision, said: “There is a consensus that there will be a drastic reduction and it’s fantastic to hear that.

“Three months would be a world-leading policy. Eventually we want a blood donation policy that is fair and tailored to each donor, but it’s all about moving towards that model.

“Although we get that heterosexual people are statistically less likely to contract a blood infection, we can’t say every gay man is a high-risk individual. We need a policy that recognises what is high risk without applying it to entire homogeneous groups.

“In all credit to the Government, they have realised this is something that needs looking at.”

The move to reduce the deferral period is supported by a working group of the Advisory Committee on the Safety of Blood, Tissues and Organs (SaBTO). An official report will be passed to SaBTO in the summer, which will then give its recommendation to the Department of Health in July.

Gay and bisexual men were asked to stop giving blood in 1983, in the throes of panic surrounding a surge in HIV infections in the gay community, and a lifetime ban was implemented in 1985.

Public Health England statistics estimate that 3,320 of the 6,095 people who were newly infected with HIV in 2015 were gay or bisexual, and 1,373 were in London.

The same report said 2,360 men and women “probably” contracted HIV via heterosexual activity, which, activists say, indicates that high risk and promiscuous sex aggravates infection levels, rather than homosexual activity.

Four people are reported to have contracted HIV through blood transfusions since 1985.

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The 1980s ban was reduced to a one-year period in England, Wales and Scotland in 2011, and in September 2016 in Northern Ireland.

It also applies to people travelling back from “high risk” countries, people who have sex with prostitutes, people who get tattoos and piercings, and drugs users who inject.

Under pressure, the Department of Health announced a review in November 2015, and last June, the SaBTO Donor Selection Working Group held its first meeting.

Dr Moira Carter, of the Scottish National Blood Transfusion Service, who is on the working group, said: “The deferral period is going to shorten considerably and [by] more than I thought.

“It’s very frustrating for gay men who are monogamous, even in long-term relationships, who are married and have children, to not be able to give blood.

“What is not acceptable is to make the deferral period longer than the risk period and to do so would be discriminatory.”

Transplant physician Dr Chas Newstead, chair of the working group, said: “The issue is the so-called window period, which is the time in which you could both contract the infection and infect another person before testing negative, and because of this, it means three months is very safe.”

However Dr Newstead said there was a minor concern that any new blood infection, similar to the Zika and Ebola pandemics, could manifest itself in the gay community first, and take the blood service by surprise.

He also said the group was wary that its new recommendation should be simple, and not confuse blood donor workers, and that there was still the “non-compliance” issue.

The 2015 UK Blood Donor Survey of 65,051 people found one per cent lie about their circumstances on their forms. Seventy-four men who have sex with men, out of 22,065, said they had been dishonest to the blood service.

The NHS Blood and Transplant Service says it needs 200,000 blood donors every year.

Labour MP and shadow minister Cat Smith, who recently raised questions in the Commons about when the review would be completed, said: “It seems daft to refuse blood from people where there is no medical evidence to show they are any more high risk.

“It also seems particularly ridiculous to still have a 12-month deferral period given the screening techniques that we have.”

A spokesman for LGBT charity Stonewall said: “Stonewall continues to push for a fair blood donation system in Britain that screens donors based on risky sexual behaviour and does not discriminate based on sexual orientation.

“Currently, gay and bi men who have not engaged in high-risk sexual behaviour cannot give blood if they’ve had sex with a man in the past year.

“A system that asks everyone the same questions to accurately assess risk of infection would increase blood stocks and create a safer supply.”

The Department of Health, in a statement first issued in February, defended the 12-month deferral period.

It said: “If a person donates blood having very recently acquired an infection they may still be in the ‘window period’ where the disease cannot be detected by the tests used for screening donated blood. If unidentified, the donation may be transfused, resulting in transmission of infection to one or more patients.

“Some infections such as hepatitis B have window periods exceeding several weeks, and on a precautionary basis SaBTO recommended 12-month deferral.