The police have warned that British high street nail salons are operating as a front for organised crime, including trafficking and slavery.

The salons – particularly Vietnamese nail bars – are using their cash-only structure to launder money from cannabis farms and prostitution. According to the National Crime Agency (NCA), they are moving child slaves between branches in order to avoid detection.

The nail bars are also linked to illegal immigration, the NCA says. The agency is currently carrying out 500 investigations into modern slavery. Albanians, Vietnamese and British nationals are the most common potential victims, the Daily Mail says.

According to Adam Thompson of the NCA’s modern slavery and human trafficking unit: “Nail bars are one of the most prevalent areas where we see Vietnamese victims, usually quite young adult males, around 18 or 19.

“The gangs… recruit them from Vietnam. People will be told, ‘Come to the UK you will get a really good job, you will be paid lots of money which you can send back to your family.’

“They will then typically use the services of an organised immigration gang… up through China then Russia and into Europe and then into the UK – usually clandestine in the back of a lorry. Then they will be linked up with the gangs in the UK who will put them to work in a network of nail bars.”

The Gangmasters and Labour Abuse Authority (GLAA) – the body that monitors modern slavery in the UK – reports that instances of shops forcing people to work for free to pay back extortionate debts have increased by 35% since last year.

Police recorded 2,255 cases of modern slavery in the last year but estimate there are “tens of thousands” of further offences that go undetected, the Huffington Post reports.

“The barbaric nature of modern slavery means it destroys the lives of its victims, which is why we introduced the world-leading Modern Slavery Act 2015 and increased the GLAA funding by £2.6 million a year to tackle modern slavery and wider labour exploitation,” Victoria Atkins, minister for crime, safeguarding and vulnerability, said in early May.