A pioneering grassroots campaign to legalise emergency contraception is launched in Honduras this week amid ongoing false claims by church leaders, senior doctors and conservative politicians that the medication causes abortions, infertility and cancer.

Honduras is the only country in Latin America where emergency contraception is banned, forcing desperate women, including rape victims, to buy expensive and unregulated contraband pills on the black market.

Emergency contraception was outlawed in 2009 just weeks after a coup d’etat backed by a powerful network of religious, economic and military elites ousted the democratically elected president. Since then, the church has played a significant role in the country’s politics.

At the time, senior Catholic and evangelical clergy publicly denounced emergency contraception as an “abortion pill”.

This falsehood was repeated by the de facto government’s health minister – a medical doctor and former president of the College of Medicine – before he authorised the ban.

Since then, teenage pregnancies have risen to one of the highest rates in the region.

The six-month campaign, Hablemos lo que es (Call it what it is), which launches on social networks on Thursday, will focus on debunking myths about the dangers of emergency contraception.

The ban in Honduras has disproportionately punished the most vulnerable women and girls, according to Paula Avila-Guillen, director of Latin America Initiatives for the New York-based Women’s Equality Centre. “The poorest women, in rural areas, and victims of sexual violence are most affected.”

Honduras has one of the highest rates of sexual violence in the world outside an official war zone, with an attack reported every three minutes in 2016.

Abortion is also banned in all circumstances, while sex education in schools is optional, and affordable family planning services are limited. The office of the first lady coordinates the national plan to reduce teenage pregnancies, which promotes abstention.

The results have been dire.

Maria, 24, had unprotected sex with her university boyfriend at a party when she was 19. It was her first sexual experience, and the couple knew little about contraception as safe sex was never discussed at school or home.

The next day her boyfriend bought emergency contraception from a pharmacy in San Pedro Sula, the country’s second largest city. Maria took the pill, which triggered a headache and dizziness, and severe menstrual pain the following month.

“I have no idea what I really took, it could have been anything,” said Maria (not her real name). “If I’d been in my village [not a big city] I’d probably have ended up pregnant.”

Over the past decade, women’s rights activists and leading obstetricians and gynaecologists have continued to press for the ban to be overturned.

Things looked up in 2014, when experts were invited by the health ministry to help formulate a protocol for victims of sexual violence. But, in 2016 officials refused to include emergency contraception. The protocol remains unpublished, despite calls for urgent action by international experts including Doctors without Borders, which runs sexual violence clinics in Honduras.

“The biggest obstacles to change are the ongoing interference of churches, and the politicisation of emergency contraception,” said Ana Falope, a psychologist and spokeswoman for the new campaign.

The law was never changed, so the ban could be overturned by a ministerial decree if there was political will. But first, activists must convince a deeply conservative society that emergency contraception is safe, and tackle deep-seated beliefs about a woman’s right to choose.

“The government and churches have used mainstream media platforms to spread fake news about emergency contraception. The first step is to break those myths, and say it how it is,” said Guillen.