The Spanish government is expected to present sweeping reforms to the country's liberal abortion laws this Friday, ushering in changes that women's groups are already calling a "serious step backwards".

While the full draft of the reforms has yet to be tabled, the ruling People's party has said it favours returning to a system where abortion will only be allowed in the case of rape or when there is a risk to the physical or mental health of the mother.

In 2010, under the Socialist government, Spain relaxed its laws on abortion, giving women the right to an abortion up to 14 weeks of pregnancy. In cases where the mother's health is at risk, or when the foetus shows serious deformities, Spanish women have until the 22nd week to end the pregnancy.

The new reforms are expected to make the procedure illegal in the case of foetal deformities and, in a reversal from previous laws, 16 and 17-year-olds will have to obtain permission from their parents to have an abortion.

The prime minister, Mariano Rajoy, sailed to victory in the 2011 elections, buoyed by promises that included a scaling back of Spain's abortion laws. Hints earlier this year of the government's intention to follow up on its promise revealed a society deeply divided on the issue, as both pro- and anti-abortion camps poured on to the streets in noisy demonstrations. The polling agency Metroscopia last year found that 81% of Spaniards were against the reforms.

"These changes have more to do with politics and ideology than social realities today in Spain," said Francisca García of the Asociación de Clínicas Acreditadas para la Interrupción del Embarazo, the umbrella group that represents 98% of the country's abortion clinics.

"From all the data we've seen, the number of abortions in Spain is actually on the decline," she said. "The People's party is trying to satisfy the rightwing factions of its party."

Given the economic crisis that has gripped the country, "there is little public demand for this initiative. These are secondary problems compared to the crisis," said García.

According to the organisation, recent data it had analysed showed that of the 118,000 or so abortions that took place in 2011, nearly 100,000 would be illegal under the expected changes.

García worries the changes could lead to "abortion tourism", with women travelling to other countries in Europe to end their pregnancies. She said the restrictions also risked sparking a public health crisis as women who could not afford to travel turned to unlicensed, illegal clinics for abortions.

Changes to the law have long been championed by Spain's Catholic church, an influential force in a country where more than 70% of the population say they are Catholic. Madrid's archbishop, Antonio María Rouco Varela, has called for an urgent reform of the 2010 law, saying it had "led to a rise in the number of abortions to terrifying levels".

It was an issue that helped propel the People's party into power, said Benigno Blanco, president of the Foro Español de la Familia. "Now it is time for the government to complete its electoral promises regarding this law. There is popular demand to do this."

In 2009, when Spain's Socialist party first floated the idea of liberalising the abortion laws, he said, a quarter of a million Spaniards took to the streets to voice their discontent. "We saw some of the biggest demonstrations in the history of the country."

He added: "I believe the government is undertaking this reform because they know that many in Spanish society will see it positively."

The expected reform has angered many in the Socialist party, who started Spain's march towards liberalising abortion in 1985 with a law to decriminalise the procedure in the case of a malformed foetus, rape, or potential mental or physical damage to the mother.

Elena Valenciano, the deputy secretary general of Spain's Socialist party, spoke out against the Catholic church in April, accusing it of trying to diminish women's say over their own bodies.

"And women, that is to say mothers, don't they have a word in this? Ministers, judges, bishops, scientists are going to decide what we should do with our motherhood. Yes, they know. We obey and shut up. Amen," she vented on her Facebook page.

Women's groups across the country echo her views. "This is a fight for control over women's bodies," said Yolanda Besteiro, president of the Federación de Mujeres Progresistas.

"For so many generations, so many Spanish women have fought for equality," she said. "They have had some tremendous successes, including a past government that counted as many female ministers as male. But now it seems like their fight was worth nothing."

On Tuesday, 200 organisations across Spain – including Besteiro's – joined forces to launch a campaign targeting female parliamentarians, asking them to stand up for women's rights. "A reform of this type suggests a lack of respect and a lack of consideration of the rights of women," said Besterio.

It was the least they could do, she said, given the serious implications of the reform. "It will take us back 40 years," she said, her voice shaking with frustration.

"It will be like Spain was during the time of Franco. It's a step back to a time we thought was forgotten."