There are an estimated 13,000 victims in Britain alone...
The UK government and the country's law enforcement agencies have vowed to make tackling modern slavery a top priority in 2017.
More than £40m is being made available to fight a crime which is estimated to have 13,000 victims in the UK alone.
In recent weeks, authorities have stepped up enforcement raids, targeting more than 280 nail bars across the UK.
Andy Radcliffe, assistant director at the UK Home Office Immigration Enforcement Agency, said: "We know from intelligence that in nail bars there is a high instance of illegal working within these businesses.
"This is in common with other cash rich sectors of the economy."
Radcliffe said the raids lead to 97 arrests, with more than 60 businesses being served with notices warning them they now face fines.
"Also, more importantly, we identified 14 individuals who may have been the subject of modern slavery," he said.
"Those individuals are all Vietnamese and have been referred into the national referral mechanism ... where they'll receive support."
Tackling modern slavery was one of Theresa May's key promises as she took office this year.
Radcliffe said there had been a steady increase in the number of suspected modern slavery cases being referred to authorities, but that it may be down to greater awareness and more joined up working arrangements between various agencies.
"Immigration Enforcement is the lead agency in that, but it brings together other agencies, such as HM Customs and Revenue, Gangmasters Licensing and the Health and Safety Executive," he said.
Modern slavery is a huge worldwide criminal enterprise, estimated to be worth more than £20bn.
When victims are discovered they are taken to special safe houses, run by charities including the Salvation Army, as part of a long period of readjustment to normal life again.
Anne Read, from the Salvation Army, said:
"It's a multi-million pound business and people will be cashing in on this opportunity they've got to feed on people's vulnerability, their hope for a better life.
"So, at the start of this experience, somebody is full of expectation, comes in to the UK expecting to work hard, expecting to receive a fair wage and then for too many of them this isn't what happens.
"They will then find themselves in a situation they can't get out of. A situation in which they are not going to be getting paid.
"They are going to be working exploitative hours and in controlled conditions and it's very unlikely they're going to get the money they were promised, money which many of them intended to send home."
For the year ahead, the UK Home Office has warned those employing or exploiting illegal workers that they can expect to see many more raids.
Complicit businesses face the prospect of heavy fines – up to £20,000 for each trafficked employee discovered.
People traffickers who supply businesses with modern slavery victims are likely to be jailed.
Additional reporting by IRN