Anti-Slavery Day: Human beings are on sale on London's Oxford Street

Despite slavery being abolished over 200 years ago, the practice still persists in the UK. According to the Home Office figures, there are up to 13,000 potential victims of modern slavery in the UK today.

Yet, only 2,340 people were referred to the National Referral Mechanism (NRM), a framework created to identify and support trafficking victims, last year. It is widely accepted that the issue is underreported, and the actual figure of victims of slavery is much higher.

Antislavery Day is held on 18 October every year. And despite the Modern Slavery Act being implemented in March 2015, campaigners warn that it remains a growing problem.

The Salvation Army sought to highlight the issue with a striking publicity stunt. Shoppers on London's Oxford Street on Friday were greeted by men and women with tags around their necks, stood silent as a salesman tried to sell his human subjects to the public.

The stunt was meant to show that slavery has not been consigned to the past, but is very much a modern issue, Salvation Army spokesman Keith Turton told Sky News.

"Many people think that slavery was abolished 200 years ago, and people think of slavery as something to do with chains and ropes and things," he said. "What we are hoping to do with this performance is to say that actually slavery has a different image these days. It is about people being used as commodities and being sold."

Data from the United Nations (UN) estimates that around 800,000 people are trafficked annually across the globe, and around 13% of them come from Europe. There are concerns that the refugee crisis in Europe could compound the issue of modern slavery, with victims being vulnerable to exploitation by criminal gangs.

The UK government has also marked anti-slavery day by announcing additional measures to tackle the growing problem in Britain. Karen Bradley, Minister for Preventing Abuse and Exploitation, said in a statement: "Modern day slavery is where one human being owns another. It is using a person as chattel."