Hundreds of people from Nigeria are being illegally trafficked to the UK where they face sexual exploitation or being forced into domestic servitude, the anti-slavery commissioner said.
Kevin Hyland said tackling the flow of people from the African country was one of his main priorities and promised to oversee work bringing together law enforcement agencies in Nigeria and Europe to get to grips with the problem.
Official figures show that more than 2,000 potential trafficking victims were referred to the authorities in 2014 - 244 of whom were from Nigeria, a 31% increase from the previous year.
The National Crime Agency statistics show the number of victims from Nigeria was second only to the total from Albania.
Mr Hyland told BBC Radio 4's Today programme: "I am extremely concerned about this. And we're talking about several hundred every year.
"This isn't just a one-off - it's continuous - so the treatment of these people, what they go through, is actually a very serious crime, so for me it's a big problem.
"But also I think the fact that there is a demand for this kind of exploitation in the United Kingdom really concerns me, that there are people who will want to buy sex, will want to exploit, will want to have children as what are current-day slaves, so that is a really serious problem."
Mr Hyland said international action was needed to address the problem.
He said: "It's about working with the law enforcement agencies in Nigeria - working with all those in the communities and telling them this could happen - and that's never been brought together before, so it's unique.
"This is a new idea - Europol, Interpol, National Crime Agency, all must work together. It's up to me to oversee this.
"This is not about lack of resources but about using them effectively."
In December, the Home Office published figures estimating there are between 10,000 and 13,000 potential victims of slavery in the UK.
They include women forced into prostitution, domestic staff and workers in fields, factories and on fishing boats.
Earlier this month, Mr Hyland warned that "Oliver Twist scenarios" are taking place on Britain's streets as children are tasked with pickpocketing, shoplifting and begging.
The former Metropolitan Police detective was appointed in November to spearhead the Government's fight against modern slavery.