Gay and bisexual men will be excluded from an NHS trial using donated blood plasma to treat people with Covid-19.
Men who have had sex with men within the last three months will not be eligible to donate blood in line with current guidelines in England surrounding blood donation, ITV News reports.
They will, however, be able to receive treatment as part of the trial.
Doctors at London's Guy's and St Thomas's Hospital are hoping to use blood plasma from recovered coronavirus patients to help treat those with the disease who are not producing enough antibodies.
But gay and bisexual men have revealed they have been told they cannot donate blood plasma to the trial, reigniting debate about the UK's blood donation guidelines, which require a three-month period of abstinence for men who have sex with men (MSM) due to an increased risk of HIV and other blood-born STDs.
Many argue that the risk assessment should be based on an individual's specific circumstances and behaviour, not just the gender of their sexual partner.
Critical care manager Andy Roberts told ITV News that he was turned down for the plasma trial after testing positive for Covid-19, despite being on a long-term monogamous relationship.
Mr Roberts' partner Keith Ward told ITV News: "It makes me feel very angry. We have been together in a monogamous relationship for more than 30 years and I previously didn’t know of this outrageous three month rule.
"It only goes to show that in the UK being gay is still thought as a form of contamination, so if you’re straight and sleep with a different person every weekend it’s safer according to [the rules]."
Laura Russell, Director of Policy at Stonewall, said: "It's really upsetting that gay and bi men who want to help in the fight against coronavirus are being prevented from doing so.
"The decision on whether people should be able to give blood or plasma should be based on individual risk assessments, not on people's sexual orientation."
The NHS Blood and Transplant service confirmed that they are using current blood donation guidelines for the plasma trial but are keeping this "under review".
"The guidelines are there to protect the health of the donor and the recipient", a statement read.
"Under the current guidelines, men must wait three months after having oral or anal sex with another man. We appreciate this deferral can feel disappointing if you want to save lives.
"Separately to the convalescent plasma trial, we are working with LGBT+ groups to explore whether we might be able to introduce a more individualised risk assessment for blood donation.”