Isabel Descals and her girlfriend raced to get hitched before Sunday's general elections in Spain almost sure to be won by the anti-gay marriage conservative opposition.

The Popular Party (PP) has appealed to the Constitutional Court against Spain's gay marriage law, which has allowed over 20,000 gay couples to wed since it was passed by the Socialist government in 2005.

Opposition leader Mariano Rajoy has repeatedly said he prefers the term "civil union" to "marriage" for same-sex unions.

"We listened to what the PP says and they are going to take a step backwards, at least when it comes to marriage because Rajoy has said he prefers civil unions," said Descals, a 40-year-old manager from Valencia.

"So we said to ourselves: 'Lets get married quickly before Rajoy eliminates our rights'," added Descals' wife, Begona Fuentes, a 44-year-old university professor.

"So I did my coming out as we say and we had a huge party on July 8."

For Descals, a civil union is of "no use".

"And what is going to happen to couples that are in the process of adoption?," she asked.

The couple's rush to marry underscores the fear in some quarters in Spain that a Popular Party government will reverse the aggressive agenda of social reforms put in place by Prime Minister Jose Luis Rodriguez Zapatero since he came to power in 2004.

When the gay marriage law, which also lets gay couples adopt children, was passed, Spain became only the third member of the European Union after Belgium and the Netherlands to allow same-sex weddings.

Zapatero also passed a "fast-track" divorce law that came into effect in 2005 that eliminated a requirement that couples be physically separate for a period before divorce proceedings can begin.

Under a law that came into effect last year, abortion became fully legalised in Spain. It was previously available in cases of rape, deformity or where the pregnancy endangered a woman's health.

The law controversially requires minors aged 16 or 17 to inform their families of a decision to abort, except if they face "a clear risk of family violence, threats, pressure or mistreatment".

"It is true that questions about what will happen to the law or how to get married have increased hugely," said Luisa Notario, head of family issues at Spain's main gay rights organisation, FELGTB.

The Socialist mayor of a small town in southwestern Spain, Jun, has even offered fast-track marriages for gay couples wishing to tie the knot before the election.

"People are very afraid, they are starting to realise that there could be a real change and they will lose a hard-won right," said Jun mayor Jose Antonio Rodriguez.

On abortion, the Popular Party has vowed in its election programme to modify the law if elected to "reinforce the protection of the right to life as well as female minors".

"What I don't accept is that a 16-year-old can have an abortion without the consent of her parents," said Rajoy on the campaign trail in a rare comment on the issue.

Ignacio Arsuaga, president of conservative lobby group "HazteOir", or "MakeYourselfHeard", that opposes abortion and gay marriage, said Rajoy avoids the topic "because there are two currents in the Popular Party -- one that wants the law annulled and another "that wants much more minor modifications".

Polls show a majority of Spaniards approve of the gay marriage, divorce and abortion laws but when the reforms were passed, protests backed by the Popular Party and the Roman Catholic Church drew hundreds of thousands out onto the streets.

Notario said she was worried but would like to think that the Popular Party "would not dare reverse the law because that would mean positioning itself, not just in Spain but also in Europe, as a party of the extreme right".

Descals said she believes that if the Popular Party changes the gay marriage law, "people would hit the streets and fight".

"I feel that there is a law today that protects me. A law that allows me to go out with my head held high," she said.