There are more people enslaved now than over four centuries of slave-trading. Little wonder as it generates 25 times the profits made two centuries ago. We must act to end this trade in misery

It is a terrible and cautionary tale. A young British woman gets duped into a modelling assignment in Milan and is then kidnapped by a gang who it is claimed wanted to auction her to the highest bidder for sex. Behind the tabloid headlines appears a sobering reminder that slavery has not gone away. This appears a case of an attempted trafficking of a UK citizen for sexual exploitation. It is also not a typical story of modern day slavery. Today’s slave tales are about the subjugation of vulnerable, often poor, people who lack basic protections afforded by a functioning legal system. Despite being outlawed in almost every nation, slavery remains a business – and the business of slavery is thriving. It is estimated that between 21 million and 46 million people are enslaved around the world. By comparison about 13 million people were captured and sold as slaves by professional traders between the 15th and 19th centuries.

Slaves today are those coerced to work or to sell their bodies or to part with their organs. They are not strictly chattel or property. Their freedom is constrained. They can be said to be effectively “owned” by an employer and treated as a commodity. They can be construction workers in the Persian Gulf, girls from Nepal trafficked into prostitution in India, or fishermen on Thai ships. Many are young children. Prostitution rings are a form of slavery. Slavery is found in homes, even in the UK, that employ domestic workers.

The reason slavery exists is that we let it – and that it we let it be so profitable. Last week the Guardian revealed research by Siddharth Kara, a US slavery economist, that showed slave traders today make a return on their investment 25 to 30 times higher than their counterparts from more than two centuries ago. With slavery’s global profits estimated at $150bn a year, it is now a criminal industry on a par with arms and drug trafficking. The outlook is bleak. Unrelieved poverty, wars, caste discrimination and gender inequality are fertile ground for slavery. Under-regulated labour markets, where for example workers cannot form trade unions, help to ensure that “wage slaves” have become embedded in –parts of the global economy.

Nations should be prepared to act. As home secretary, Theresa May modernised Britain’s slavery laws, bringing in fines and creating an anti-slavery commissioner. This was a welcome step. As prime minister, Mrs May invoked the spirit of campaigners such as William Wilberforce, who led Britain in the fight against slavery 200 years ago. But she also introduced a visa system tying migrant domestic workers to employers. In the words of one Tory critic this has made the government “complicit” in a form of enslavement. Mrs May’s contradictions do not end there. Her Brexit would mean Britain leaving the jurisdiction of the European court of justice – and limit collaboration with EU states to fight slavers.

Where Britain could make a difference is to recognise that slavery is where morality and the law meet. It is morally wrong and hence currently illegal for a UK company to extract profits from workers operating as slaves in this country. Why, as leading barrister Parosha Chandran argues, can “profits obtained from the slavery and extreme exploitation of workers (abroad) filter home to the UK company, crime-free”? The government should be able to prosecute those who profit – through contractors or wholly-owned subsidiaries – from slavery abroad. Such extra-territorial legal reach helps to sanction companies that use bribes abroad or to stop child sexual exploitation by British paedophiles in foreign nations. Mrs May could also take a leaf out of President Obama’s book with a ban on importing goods made by children or slaves. It is instructive to note that in the 1930s when US states refused to enact provisions to end child labour, president Franklin D Roosevelt got rid of it by preventing the interstate trade in goods made by children. Trade should not be built on slavery. It’s a matter of conscience. We must stir ours to stop a crime against humanity.