The issue of modern slavery has been in the spotlight recently, after three women were freed from a south London house in November. They had allegedly spent three decades as slaves, with a Maoist cult apparently at the centre of the story.

The story led the Sun to publish a front page headline: “Britain’s 5,000 slaves”. Claims about the number of people living in conditions that can be described as "modern slavery" can vary: the UK Human Trafficking Centre, part of the National Crime Agency, identified 2,225 potential victims of human trafficking (just one of the forms of exploitation covered by definitions of modern slavery) in 2012. Of course, these thousands of other cases are generally less headline-worthy than the three women rescued last month: people trafficked from Vietnam to work in cannabis farms in suburban Britain. Women sent to the UK from India, Pakistan, and Bangladesh to marry British citizens, forced into domestic servitude. Women trafficked from Eastern Europe for the sex trade, men for forced labour.

Two months before the south London case, the home secretary Theresa May had announced that she would launch a new law on modern slavery, saying it was “scarcely believable” that this still happens in Britain today. "Vulnerable people from all over the globe are trafficked into Britain every day," she wrote in the Sunday Times. "Most end up working as modern-day slaves, without pay, without rights and without hope."

This week, the Home Office announced that this draft anti-slavery legislation is set to be published, along with a report on the issue by Labour MP Frank Field. Writing in the Times, Field said that an estimated 10,000 people are living as virtual slaves in the UK, working in the sex trade, agriculture, food processing, and as domestic staff – interestingly, doubling the estimate given by the Sun. The forthcoming Modern Day Slavery Bill will draw together all existing laws on trafficking into a single piece of legislation. It will also increase the maximum sentence from 14 years to life, and will create the new role of anti-slavery commissioner to hold law enforcement agencies to account. It is hoped that the bill will increase convictions for trafficking and enslavement offences, which tend to be in single digits each year.

This brings us back to the question: what is modern slavery? While traditionally, slavery referred to the sale and total ownership of humans, the meaning has evolved over time. Anti-Slavery International’s definition of modern slavery, lists a range of conditions, including being forced to work through mental or physical threat, and having freedom of movement constrained.

Arguably, it is precisely because the victims of slavery in modern Britain are so diverse, that broad-ranging legislation is required. But of course, this is only half the battle – as Field acknowledges, “no country has beaten modern slavery with criminal legislation alone”. While reporting on immigration and asylum issues, I have met women who have endured years of domestic abuse and forced labour after being sent to the UK as brides. I’ve also met countless people of both genders who have fallen into situations that amount to slavery after having their asylum cases refused and being forced into destitution. Particularly in the latter category, these people were not trafficked. One Somali woman I know - who had come here to seek asylum during the country’s civil war – worked as a domestic servant, sleeping on the floor in a damp basement. But she was grateful. The couple enslaving her had given her shelter when no-one else would. Her case is far from unique. Most people with uncertain immigration status – whether they are trafficked or seeking asylum – are terrified of going to the authorities in case they face prosecution or deportation. Time and again, this is used as a means of psychological control.

While coherent legislation on forced labour and trafficking (and more effective enforcement) can only be a good thing, the problem cannot be addressed without simultaneous action to tackle injustices within the immigration system and to protect the most vulnerable.