It is expected to be voted on by lawmakers in January, and observers believe the law is almost certain to pass, as left-wing parties who are supportive of gay marriage occupy a majority of seats.
If it’s approved, Portugal’s conservative president can ratify or veto it, a move that can be overturned by Parliament. If there’s no veto, the first gay marriage ceremony could take place in April.
Previous efforts to introduce gay marriage have run into strong resistance from religious groups and conservative lawmakers in the overwhelmingly Roman Catholic country.
Gay marriage is currently permitted in five European countries — Belgium, the Netherlands, Spain, Sweden and Norway.