US Massachusetts Senator Elizabeth Warren has urged for America to allow gay and bisexual men to donate blood.

Senator Warren says she only learnt of the ban by speaking to a Boston resident who wanted to donate in the aftermath of the city’s bomb attack.

The Democrat was among 86 members of Congress to sign a letter urging for the ban to be lifted by the Health and Human Services (HHS) Department on Thursday.

Leading gay politicians who added their names to the letter included: Senator Tammy Baldwin, Congressman Mark Takano, Congressman David Cicilline, Congressman Sean Patrick Maloney and Congressman Mark Pocan.

The HHS has commissioned several studies that are designed to assess reforming existing donation rules.

“For me, this has been a basic issue of fairness and of science – blood donation policies should be grounded in science, not ugly and inaccurate stereotypes,” Senator Warren said in a statement.

“When a Massachusetts man told me he wanted to donate blood during the bombings but couldn’t because of his sexual orientation, I dug deeper into this discriminatory ban and I didn’t like what I found. Current policies are contrary to science.”

The American Medical Association (AMA) voted to reject the federal blanket ban in June.

The policy was introduced in 1983 in response to the AIDS outbreak, when little was known about HIV.

In 2011, England, Wales and Scotland introduced a one-year deferral for gay and bisexual men who wish to donate blood.

They can donate – providing they refrain from having sex with men for 12 months.