Pope Benedict XVI sent a message of support yesterday to a family values rally of Catholics in Madrid, saying a family was "founded on the marriage between a man and a woman."
In a special Spanish-language address from Vatican City before Angelus prayers, the Pope addressed the thousands gathered at the Plaza de Lima in the Spanish capital.
One of the greatest services Christians could perform was to raise a "family based on marriage between a man and a woman... because it is of paramount importance for the present and the future of humanity," he said.
The Pope's message was broadcast live on giant screens to the gathering in Madrid.
Cardinal Antonio Maria Rouco Varela, the Archbishop of Madrid, told the crowd that the traditional family was threatened by the acceptance of "different models of families".
Gay marriages have been legal in Spain since 2005, when Socialist Prime Minister Jose Luis Rodriguez Zapatero's government legalised it during his first term in office.
The Archbishop also attacked the Bill currently going through Parliament that liberalises the abortion law.
In the face of fierce opposition from Catholic activists and the right-wing opposition Popular Party, Socialist deputies voted it through the lower parliamentary chamber on December 17. The Senate will consider it in the new year, before it returns to the lower chamber for final approval.
If, as likely, the Bill passes into law, abortions would be allowed on demand up to the 14th week of pregnancy and up to 22 weeks if there is a risk to the mother's health or if the foetus has serious problems.
This is in line with most of Spain's European Union partners.
Spain's existing law permits abortion only in cases of rape, foetal malformation or when a pregnant woman's mental or physical health is deemed to be at risk if the pregnancy goes to term.
The last argument is used for the great majority of abortions carried out in Spain.
The Archbishop of Madrid and the Catholic lay organisation Camino Neocatecumenal organised yesterday's event to defend the Catholic conception of families against the line taken by the Socialist government.