The anti-discrimination chief has told the government it will inevitably have to address the issue of same-sex marriage after it was legalised by a string of countries elsewhere.
But Dr York Chow Yat-ngok said that in Hong Kong's traditional society, civil union - a status short of marriage that carries most of the legal rights of marriage - could be an alternative.
His remarks yesterday drew a cautious response from the Constitutional and Mainland Affairs Bureau which said the issue was "hugely controversial" in Hong Kong society and would require prudent handling.
"In many comparatively advanced and open countries all over the world, even some with strong religious backgrounds, such legislation has been made, despite all the controversies," Chow, chairman of the Equal Opportunities Commission, said on RTHK. "They considered it necessary from the perspective of the society as a whole," he said. It was the first time he had spoken on the issue in public.
Acknowledging that religious bodies and some traditional families considered marriage as a union between a man and a woman, "not man-man, or woman-woman", Chow added: "It is worth consideration whether 'civil union' can replace marriage. The imperative consideration is that the legal status should be similar to that of marriage."
The government has been criticised by gay-rights activists for procrastinating on developing laws protecting and empowering sexual minorities known as LGBT, or lesbian, gay, bisexual and transgender people.
Some in the LGBT community welcomed Chow's suggestion on civil union, saying it would be unrealistic for Hong Kong to discuss gay marriage at this stage, despite laws passed in countries including New Zealand and France and by the UK government for England and Wales.
These were in addition to a recent US Supreme Court decision that same-sex marriage must be reinstated in California and that in states that recognise such marriages, gay couples must have the same tax and inheritance rights that man-woman couples enjoy.
Calling the issue "hugely controversial", the Constitutional and Mainland Affairs Bureau said that while some could see it as maintaining equal opportunities, there were others "who are concerned about a clash with core family values, religion and education if the government launched a relevant consultation". It said the government would handle the issue "prudently".
Raymond Chan Chi-chuen, Hong Kong's first openly gay lawmaker, welcomed Chow's remarks but was dissatisfied with the government response, because civil union was not so controversial to handle.
The Catholic Church could not be reached for comment.