South Africa is one of the many countries in the global south that is host to a vibrant "sex workers' rights" movement, calling for full decriminalisation of the sex trade.

But in Cape Town at least, this popular narrative is being increasingly challenged by survivors of prostitution, feminist abolitionists and human rights activists, under the banner of Embrace Dignity, an NGO founded by former health minister Nozizwe Madlala-Routledge.

A former ANC activist, Madlala-Routledge has devoted much of her life to ensuring women get their full rights in South Africa. A member of Parliament from 1994 to 2009, and Chair of the ANC Parliamentary caucus, on leaving politics she wanted to put her experience To good use.

In 2009 Madlala-Routledge was invited to NYC to give a presentation to NoVo, a women's human-rights organisation, on the topic of trafficking and prostitution in South Africa. The Fifa World Cup was due to be held the following year, and the pro-prostitution pressure organisation Sex Worker Advocacy Taskforce (Sweat) had called on the government to speed up the decriminalisation of prostitution, claiming that it would solve the problems inherent to the sex trade, and offer protection for those involved.

"Being a Quaker and a feminist I should have naturally have been arguing for the abolition of the sex trade," says Nozizwe when we meet in the Embrace Dignity offices in Woodstock, Cape Town, "but I had swallowed the line about women having control of their bodies [and that] prostitution is the oldest profession."

Madlala-Routledge had already begun to worry that the World Cup would provide an ideal opportunity for criminal gangs to traffic women into and around the country to meet the demand of the thousands of male spectators and participants.

"Almost everybody else was talking about how fantastic this opportunity was for South Africa," says Madlala-Routledge, "but I knew it meant bad news for women and girls."

In conducting her research for NoVo, Madlala-Routledge discovered that the loudest voices were calling to decriminalise not just the women and men in prostitution, but also the pimps, brothel owner and sex buyers.

Preparing for her flight to NYC, Madlala-Routledge picked up a book entitled The Idea of Prostitution, a convincing argument against the acceptance and normalisation of the sex trade by the feminist scholar and feminist abolitionist, Sheila Jeffreys.

"I had no idea how it had even come to be on my shelf," says Madlala-Routledge, "but I read every word, and when I arrived in NYC I tore up my presentation [which otherwise would have been far more accommodating of the argument that blanket decriminalisation was the only way to eradicate the harms] and delivered a very different one. When I got back to Cape Town I began to focus on campaigning for abolition."

In 2011, Embrace Dignity was registered as an official NGO, and today it is thriving, with new volunteers knocking at its door every month, and a sway of prostituted women, and those who have left the industry, coming to them for help and advice.

As well as offering support to women to exit prostitution, and running education and awareness programmes in schools, townships, and for the general public, Embrace Dignity campaigns to change the current laws on the sex trade in South Africa.

"We look at the philosophical foundations of the Nordic law [where those selling sex are decriminalised, and sex buying becomes a criminal offence], says Madlala-Routledge, "It explained prostitution is seen as gender based violence in Sweden, and how the law needed to treat buyers and sellers differently because, in the main, women forced or coerced by poverty and gender inequality, so therefore any criminal sanctions should be focused on the buyers, and the women should be helped to exit."

But Embrace Dignity has yet to convince the majority of funders and politicians that their approach is the correct one. Sweat has been active across South Africa since the early 1990s, and is generously funded by George Soros' Open Society Foundation.

At the Embrace Dignity offices I meet Dudu Ndlovu, a gender studies student who was previously a volunteer at Sweat. I ask what had led to her shifting positions and becoming sympathetic to the abolitionist position.

"What's amazing about the work we're doing here is that we really are pushing for actually reducing harm, like truly, honestly reducing harm and exposing the fact that there is an alternative. It is a comprehensive view, and it is really the truth."

Mickey Meji has worked with Embrace Dignity for three years, and was also formerly involved with Sweat, both as a volunteer and as a paid worker.

"Initially when I joined Sweat it was the only organisation willing to work with women who are prostituted, except they called us 'sex workers'," says Meji. "Since I was on the street and I couldn't speak with anybody about this, I felt I had found a space for the very first time where I could actually be myself and talk about things I hadn't talked about with any person."

Meji eventually realised that pro-prostitution organisations tend to be led by the available funding rather than concern for those involved in the sex trade. "The big funders are willing to fund decriminalisation of prostitution," says Meji, "and the idea that prostitution is simply 'sex work'. It is not though, it is abuse of women."

At Sistahood – a support group for women wishing to leave the sex trade, set up by Embrace Dignity – Meji stands by a whiteboard, scrawling random words and sentences shouted out by the 20-plus women sitting around a large table. "Prostitution must fall", "Education must rise", and "Women and girls and not for sale", they shout.

The women, mainly black South Africans, all have stories of violence from pimps, sex buyers and police, but they are also visualising a future free from prostitution. Many are keen to campaign for the introduction of a law to criminalise the demand.

"These men [sex buyers] have a comfortable life," says one of the women, "after they have done with us they go back to their homes and their wives. We want them to be exposed and for it to be known that this is what they are doing."

On my last day in Cape Town I meet Madlala-Routledge for coffee, and ask her what are her future plans for Embrace Dignity. She tells me, in her soft but authoritative voice that the biggest challenge is to educate society and raise awareness about the truth of the sex trades, and of what prostitution represents for poor, black women.

"Mandela would understand," says Madlala Routledge, "I seriously believe that if we had gone to him to open his eyes, he would have been on our side saying, 'the nation is not free while women remain in oppression, while poor women, especially marginalized women remain in such dire oppression, dire poverty.'

"We are not free, and that's what drives me. I can't really enjoy my freedom and my rights while others are held in the captivity of prostitution."