While the extent of the slavery is hard to measure, the 2016 Global Slavery Index suggests there are 45.8 million people around the world who remain victims of this crime: from debt bondage and human trafficking, to forced labour and child exploitation. In Australia, at least 4300 people are said to be enslaved by criminal syndicates forcing them into prostitution and work. The genesis of Melissa King's investigation was complaints about a Queensland contract labour supplier, Emmanuel Bani, an ex-Papua New Guinea cop with a dark past. Bani had been implicated in an international timber smuggling operation and allegations of police corruption a decade before. Now, he was suspected of supplying migrant workers to farmers in the Townsville region, only to pocket all or most of their pay and threaten those who complained with violence. "They were left with no money, no food in a foreign company away from their families and were treated no better than slaves," she says. The case highlighted the impunity enjoyed by figures such as Bani, even after they were hauled before a court. But it is also emblematic of a much bigger problem: the astonishing fact that there are now more people trapped in slavery around the world than any other time in human history.

An Australian Modern Slavery Act, modelled on the UK laws of the same name, is supposed to help combat this. Proposed legislation announced last week will compel large companies to report annually on their efforts to safeguard supply chains from slavery, with the details placed on a public repository. In theory, it means that supermarkets stocking the fruit Bani's workers picked would have needed to audit the farms on which they worked, hopefully detecting and deterring the exploitation. Some Australian companies claim to already do this but with mixed results, partly because evidence of exploitation can be hard to detect. Justice Minister Michael Keenan wants large companies to make annual Modern Slavery Statements. Credit:Alex Ellinghausen Take, for example, a winter jacket bought at your local retail chain. The label might say "made in Japan" but in pursuit of cheap labour, the fabric might come from child labour in India, the buttons from a sweat shop in China, the zipper from Taiwan. Just last year, Fairfax Media exposed Rip Curl selling supposedly Chinese-made ski jackets that were made in North Korea, where workers are routinely exploited.

Melbourne University researcher Kate Nicholl warns that complex, offshore supply chains expose many Australian businesses to the possibility they are benefiting from slavery. Most welcome the idea of a Modern Slavery Act with an anti-slavery commissioner to investigate complaints, but as Nicholl and others told a parliamentary inquiry this month, its effectiveness depends on the detail. One concern about the UK legislation is that the reporting threshold for companies sits at £36 million – the equivalent of about $58 million. So when Justice Minister Michael Keenan announced on Wednesday that only large companies with yearly turnovers of at least $100 million may be required to make annual "slavery statements" – without penalties for non-compliance or a clear commitment for an independent watchdog – many were unimpressed. Human trafficking expert Anne Gallagher warns that any Act that merely tacks onto Australia's existing and poorly enforced human trafficking and workplace laws will fall short of expectations. After all, Australia has slavery provisions in the Commonwealth criminal code, yet according to the government's own figures, 604 trafficking and slavery-related cases were investigated or referred between 2011 and 2016 – and only seven convictions were made.

Former Cambodian slave Sophea Touch gave evidence to a modern slavery inquiry in Melbourne this month. Credit:Luis Enrique Ascui National Union of Workers of president Caterina Cinnani says part of the problem is that victims often won't complain for fear of reprisals. A Modern Slavery Act could help – since the introduction of the UK legislation in 2015, there has been a 63 per cent increase in the number of victims coming forward – but as Cinnani points out: "Laws made to protect workers fall apart if they can't be enforced." The need for better protection was also a common theme among the victims Fairfax Media spoke to for this feature. Among them was was 28-year-old Amin*, a Rohingya worker who endured slave-like conditions on an asparagus farm in Melbourne for a boss who withheld his pay and threatened to beat him with stick when he begged for his money. Another was Sophea Touch: abandoned by her parents at the age of four; put to work selling cakes in a Cambodian village; abused and starved by the families who traded her. Years later she managed to escape with the help of Australian charity Hagar, but her story – tearfully recounted this month before a modern slavery parliamentary inquiry – will haunt her forever. "Every day I lived with fear," she says. "I felt so hopeless."

And then there's Filipino housekeeper Aurora**, who arrived in Canberra with the hope of a new job working for a foreign diplomat. But as authorities would later hear, the employer took her passport, prevented her from speaking to anyone or leaving the house, and paid her only $300 a month to work from Monday to Sunday, between 6am to 10.30pm – much less than the $2500 a month stipulated in her contract. "Even when I went to throw the garbage out, I had be accompanied by his wife. I was like a prisoner," she says. Human trafficking advocacy group Project Respect has joined the chorus of those demanding new laws aimed at people who knowingly or recklessly use or employ trafficked workers. Human trafficking is an ongoing problem in the sex industry. Credit:Janie Barrett By scouring online brothel reviews, Project Respect has found anecdotal evidence of brothel clients suspecting sex workers are trafficked but failing to act on this suspicion. One brothel user said that despite having such a concern of an Asian sex worker, he still "banged her rotten."

Stronger evidence that employers may be turning a blind eye to human trafficking has emerged in sex slavery prosecutions arising from inquiries by the federal police. On Victoria Street in Richmond, a few hundred metres from Vietnamese soup kitchens and upmarket bars, is the Candy Club brothel. While there is no evidence the women at the Candy Club are trafficked, the venue's madam, Lin Gao, was implicated in a major sex trafficking inquiry by the federal police in 2012 involving a South Melbourne brothel. Despite this, the Victorian government continues to license Gao's Richmond brothel. When called this week by Fairfax Media, Gao refused to talk. But as a small business owner, she won't be bothered by the Coalition's proposed reforms. Back in Canberra, momentum is building – but how bold will Australia be? Business leaders such as billionaire Andrew "Twiggy" Forrest this week trumpeted a proposed anti-slavery regime based on supply chain transparency. Labor spokeswoman Clare O'Neil welcomed the step but warned that without penalties and an independent watchdog, any plans would be toothless.

And on Thursday, a joint sub-committee quietly tabled a report calling on the Coalition to go much further. It suggested a new Act, a slavery watchdog, supply chain scrutiny, and government procurement reporting. "We have a unique, once-in-a-lifetime opportunity to take the lead in stamping out modern slavery," Liberal chair Chris Crewther told parliament. "Let us not miss it." * surname withheld. ** not her real name.