It’s a scorching afternoon in Buenos Aires. Most men that you pass in Mataderos, a neighbourhood on the edge of the city named after the cattle abattoir that once stood here, have shed their shirt. They sit in plastic chairs under awnings, languidly passing the day sipping beer, their eyes occasionally catching on a passing woman’s hemline. Nearby, Jorge Taddei is sheltering from the worst of the summer heat in his air-conditioned home, smoking a cigarette at his dining-room table.

“I would love for Vázquez to be free. For my daughter to still be alive. For them to be happy together,” he tells me. “She was deeply in love with him.”

Taddei and his wife, Beatriz Regal, suspected that Eduardo Vázquez, a drummer with a wild streak and a controlling nature, would be bad news for their teenage daughter Wanda, so they tried to keep the couple apart.

Emboldened by their belief in their star-crossed fate, the pair were married a decade later anyway. By then, Wanda was a young mother-of-two (the children are the product of a previous marriage) and Vázquez was a rock star, a former member of the nationally famous band Callejeros.

The marriage was brief and quarrelsome. On 10 February 2010 Vázquez doused Wanda in alcohol and set her on fire. She died 11 days later from her injuries.

Vázquez’s celebrity and the brutality of Wanda’s murder brought unprecedented media attention to a long-standing problem in Argentina: femicide. On average, one woman is killed every 30 hours, by a partner, former partner or some other close figure, because of her gender.

“Wanda’s case was a wake-up call for Argentinians,” says Alejandra Perdomo, a film-maker whose documentary Cada 30 Horas (“every thirty hours”) sheds light on violence against women in the country. “It was a trigger for us to stop calling gender violence a ‘crime of passion’ and to start calling it ‘femicide’.”

Domestic abuse is often still considered to be a normal flaring up of passions – perhaps just a lovers’ quarrel – that can be resolved behind closed doors. However, activists such as Taddei and Regal are fighting to change this perception. Today, they lead the Wanda Taddei Institute, which trains women to assist victims of domestic violence looking to file police reports – a difficult and humiliating process, given that law-enforcement agencies routinely ignore women or turn them away.

The couple remember the struggle they faced trying to get justice for their daughter from a judiciary unable to see beyond its own machismo. “On the first day in court, Vázquez started crying and going on about how it had all been an accident, that he and Wanda shared this sublime love,” Taddei says.

“And the judge stepped down to console him in front of us,” Regal adds.

In September 2013 Vázquez was given a life sentence – 35 years in Argentina – but only after Wanda’s parents insisted on appealing a less exacting June 2012 ruling that gave him 18 years. The judges presiding over the case had cited a state of so-called “violent emotion” at the time of the murder as an extenuating circumstance.

Public outcry over the initial ruling directly led Argentina’s Congress to pass legislation in November 2012 imposing longer prison sentences for gender-based murder. Yet despite harsher sentencing and greater media attention, the number of femicides has slowly crept up in recent years.

According to the NGO Mujeres de la Matria Latinoamericana (“women of the Latin American motherland”), in 2016 there were a record 322 gender-based murders, and since the start of 2017 the historic average of one woman killed every 30 hours has jumped to one every 18.

“We’re seeing a violent, neo-chauvinist reaction,” says the journalist Florencia Alcaraz, one of the founders of the Ni Una Menos (“not one less woman alive”) collective, the face of a powerful feminist movement in Argentina today.

Ni Una Menos was formed in 2015 and staged a 400,000-strong rally in June that year. It has since grown into an international network, with sister chapters throughout Latin America as well as in Italy and Spain. It was instrumental in organising an international women’s strike on 8 March 2017.

The group’s chief demand is state action. A comprehensive law promoting the prevention, penalisation and eradication of violence against women was rolled out in 2009, but policymakers have given the problem little or no attention since. Plans to build more women’s shelters and set up additional telephone hotlines have come to nothing, as has a much-touted national registry recording every instance of gender violence.

The conservative Mauricio Macri has been president of Argentina since 2015. Recently, his administration cut 67 million pesos (£3.5m) from a gender violence prevention fund, leaving little more than eight pesos (approximately 40 pence) per woman.

However, both Ni Una Menos and Wanda’s parents argue that the state’s most damning failure is its refusal to enforce a 2006 law providing for a nationwide sex education curriculum. In addition to providing information on contraception and safe sex, the programme includes vital content on reversing sexism and combating discrimination.

“We need to talk about gender in kindergarten, elementary school, secondary school, and so on,” Taddei says. “If we start with the little ones, within four or five generations, we’ll start to change the social paradigm.”

When it comes to public policy, the women of Ni Una Menos aren’t holding their breath, but they do take small comfort in what they see as the start of a cultural shift.

“The tolerance bar for machismo has gone down,” Alcaraz says. “Women are realising that domestic abuse is not natural and isn’t something they should have to live with.”

Back in Mataderos, the sun is setting. The men abandon their posts and bring the chairs in. “The statistics will go down,” Taddei says firmly. “But it will take a long time.”