Desmond Tutu has urged Uganda’s President not to sign a harsh Anti-Homosexuality Bill that could see same-sex couples sentenced to life in prison.
South Africa’s retired Archbishop compared Yoweri Museveni's behaviour with Hitler's in Nazi Germany.
Although the President had pledged not to sign the bill, last week he reconsidered and said he would approve the legislation after he consulted scientists who said homosexuality was "learned."
Tutu, a Nobel Peace Prize winner, said he was “disheartened” by Museveni's decision because there is "no scientific basis or genetic rationale for love."
He said Museveni's decision could lead to situations like those that happened in Nazi Germany or during the apartheid.
"In South Africa, apartheid police used to rush into bedrooms where whites were suspected of making love to blacks," Tutu said in a statement. "It was demeaning to those whose 'crime' was to love each other, it was demeaning to the policemen - and it was a blot on our entire society."
"The history of people is littered with attempts to legislate against love or marriage across class, caste and race," Tutu argued.
"But there is no scientific basis or genetic rationale for love... There is no scientific justification for prejudice and discrimination, ever. And nor is there any moral justification.
"Nazi Germany and apartheid South Africa, among others, attest to these facts."
And he urged Museveni to strengthen Uganda's "culture of human rights and justice."
The President's indication of approval for the bill prompted widespread condemnation from Western governments.
U.S. President Barack Obama said in a statement that the bill signals a "step backward for all Ugandans" and warned that enacting it would "complicate" the East African country's relationship with Washington.
The bill is popular in Uganda, where it has been championed by Christian clerics and politicians who say it is necessary to deter Western homosexuals from "recruiting" Ugandan children.
It originally proposed the death penalty for a category of offenses called "aggravated homosexuality," defined to include repeated sex among consenting adults as well as sex acts involving minors or a partner infected with HIV.
Amid international pressure, including the threat to withdraw aid by European countries such as Sweden, the death penalty was removed.
The bill before Museveni sets life imprisonment as the maximum penalty and imposes a 14-year jail term for first-time homosexual offenders.
Additional reporting by Associated Press