The equal marriage legislation passed in this parliament will bring happiness to many couples who, for the first time, regardless of sexual orientation, can marry the one they love. For LGBT people across the UK, a social revolution has taken place. Bullying and stigma about homosexuality has been reduced and equality has become more of a reality. But the cause of equality still has barriers to break.

If you are a gay man and have not been celibate for 12 months or more, you are banned from donating blood, even if you have been practising safe sex. By contrast, if you are straight but promiscuous with multiple partners and practising unsafe sex, you can. This is wrong.

Until 2011, it was forbidden for a gay man to donate blood. The ban was imposed during the Aids epidemic of the 1980s when it was believed the gay community was disproportionately affected by the disease. Now it is recognised that many other groups of people are also likely to have a higher than average proportion of HIV infection.

In less than 20 years, society has seen the equalisation of the age of consent, the ability for same-sex couples to marry or enter into civil partnerships, the banning of discrimination against homosexuals in all walks of life, and a revolution in how we see sexuality in 21st century Britain. Each step forward for a gay person has been fought for, and I believe much of the opposition we have witnessed in recent years to gay marriage will one day seem as out of touch as opposition to the compulsory use of seatbelts in the 1970s does now.

Yet, against this background of huge social change in the cause of equality, it is still forbidden for a sexually active gay man to donate blood. Is it based on science? Or on the 1980s view of HIV and Aids?

Thankfully, HIV is no longer the killer disease it once was, though it still cannot be cured. But its detection is almost instant, so anyone infected can be prevented from donating blood. HIV is not unique to gay men; it is prevalent in straight people too. If a gay man practises safe sex and can prove he does not have HIV, why should he not be allowed to donate?

Giving blood does not just involve HIV issues – there are concerns about syphilis and hepatitis B too. Hepatitis B does tend to affect the gay community more than other groups and is transmitted in a similar way to HIV. So the logic still stands: if a gay man is practising safe sex, why should it be right to ban him from blood donation but not a straight man who has been promiscuous? The logic and the science do not add up.

In January last year, parts of England and Wales came within three days of running out of a blood group. With outdated, illogical and unequal rules for blood donation, such crises are likely to recur. The rules on blood donation need to be changed to reflect modern medical science. Safety for donors and recipients of blood transfusions must of course be respected, but fairness and equality need to be considered too.

I shall be seeking further scientific advice on this, but I believe it to be one of the last frontiers of equality and intend to raise the issue in parliament.

Twitter: @Mike_Fabricant