A controversial law that would give gay and lesbian couples the same right to marry, divorce and adopt children as heterosexuals was approved by Spain's Socialist government yesterday.
The draft legislation, which now goes to parliament, has sparked a furious reaction from the Roman Catholic church, which warned that it risks "introducing a virus into society".
However, polls show the move enjoys firm support from the country's increasingly liberal population.
The law will make traditionally Catholic Spain only the third country in the world to legalise gay marriage after the Netherlands and Belgium. Some other nations have provisions for recognising committed same-sex unions.
"We are putting an end to centuries of discrimination... Spain is now in the vanguard of Europe and the world in fighting this discrimination," Deputy Prime Minister Maria Teresa Fernandez de la Vega told a news conference.
The move seals a remarkable transition since the 1975 death of dictator Francisco Franco, who banned homosexuality.
The minority Socialist government is almost certain of getting the bill through parliament with support from small groups, gay activists say.
Even the main centre-right opposition party has said it supports legalising some form of gay unions, although it does not believe they should be the same as heterosexual marriages.
In the US, where same-sex unions have become a controversial issue, both President George W. Bush and challenger John Kerry say they oppose gay marriage.
Activists say the government made a pioneering choice in opting to change Spain's existing civil code to cover gay couples, rather than creating a separate law to govern same-sex unions, which could have led to more subtle discrimination.
Particularly important to many couples, but among the most controversial implications of the law, is the right to adoption.
"There are already thousands of children in Spain who live with homosexual parents... more than 50 studies agree that there are no differences among children who grow up in homes with homosexual parents," Fernandez de la Vega said.