Spain’s Federation of Gays and Lesbians held a protest outside the headquarters of the country’s main opposition party on Saturday.
Mariano Rajoy, who leads the conservative Partido Popular (PP), said in an interview last week that he is ready to take he right to adopt away from gay couples.
Prime Minister Jose Luis Rodriguez Zapatero has called a general election for March 9th.
The campaign proper runs for the two weeks leading up to the poll, in effect political parties have been electioneering for months.
Antonio Poveda, president of the Federation of Gays and Lesbians, accused PP of homophobia.
“We’ve fought hard to achieve equal rights and are appalled by this party’s stated wish to turn the clock back to Spain’s repressive past,” he said.
Latest opinion polls from Angus Reid Global Monitor show 40.2% of respondents supporting Mr Zapatero’s Socialists, with 38.7% support for PP.
The Zapatero government came to power in the aftermath of the 2004 Madrid train bombings in which 191 people were killed by Muslim terrorists.
It has legalised same-sex marriage and adoptions, eased divorce laws and repeatedly clashed with the Roman Catholic Church.
PP has promised to establish a new “family” ministry if they win the elections next month and suggested that the “traditional family” needs extra protection.
Despite their appeals to devout Spaniards and their conservative stance, PP has not indicated they intend to amend or abolish gay marriage should they come to power but may “downgrade” them to civil partnerships.
The Roman Catholic Church has been accused of interfering in the political process in recent months.
Spain’s ambassador to the Vatican met with Church officials earlier this month to protest about interference in the country’s elections by the country’s bishops.
Foreign Minister Miguel Angel Moratinos revealed that Ambassador Francisco Vazquez expressed his “perplexity and surprise” at statement issued last week by the Spanish Bishop’s Conference.
“Catholics may support and join different parties it is also true that not all (electoral) programmes are equally compatible with the faith and Christian demands in life,” the bishops said.
This was widely interpreted as an instruction to the faithful not to vote for parties that support gay marriage or negotiate with Basque terrorists.
At the end of December Pope Benedict XVI addressed a “family values” rally in Madrid by a videolink from Rome.
He told the crowd, estimated at 150,000 people, that the family is “based on the unbreakable union of man and woman and represents the privileged environment where human life is welcomed and protected from the beginning to its natural end.”
The rally was supported by PP.