A former top PSNI officer has revealed how modern slavery and human trafficking in the UK is "far more prevalent than previously thought".
A report by the National Crime Agency (NCA) shows that hundreds of cases affect every large town and city.
Will Kerr, the former PSNI Assistant Chief Constable, warned the threat of human trafficking is continuing to expand as the number of suspected victims has more than doubled in three years.
Mr Kerr, now the NCA's vulnerabilities director, said there are 300 live police operations targeting modern slavery, with alleged victims as young as 12 being sold to families in the UK from Europe.
"The more that we look for modern slavery, the more we find evidence of the widespread abuse of the vulnerable," he said.
"The growing body of evidence we are collecting points to the scale being far larger than anyone previously thought. This should not be acceptable in any way, shape or form."
Mr Kerr's comments come as the NCA launches an advertising campaign raising awareness of the signs of modern slavery in everyday life.
There were 3,805 people reported as potential victims in 2016, an increase from 1,745 in 2013, according to NCA statistics.
Mr Kerr left his role in the PSNI in November last year after being offered a temporary post as director of NCA's Child Exploitation and Online Protection Command.
He said the most common nationality of victims brought into the UK were people from Eastern Europe, Vietnam and Nigeria.
But he also cited one example of a 12-year-old Roma girl being stopped at border control, bound for a life as a domestic slave.
He said: "She was being brought in to work for a family in part of the UK, where she had effectively been sold by her father - or it had been facilitated by her father - and she was being brought in to take this family's children to school and pick them up every day, and clean the house in between.
"Twelve years old, same age as my youngest son."
Mr Kerr said criminal charges were pending against those involved in the case.
But he said it underlined the sheer scale of the problem authorities were facing, further complicated by the fact some people do not realise they are a victim of slavery.
He added: "People are being exploited on an hourly and daily basis.
"The full scale and extent of it, we don't know. But what we have found is that in every medium-to-large town and every city in the UK, we have found evidence of vulnerable people being exploited.
He said there were "lots of different outlets" for people trafficked into the UK to be working illegally and against their will.
Mr Kerr said examples included those working at car washes and in construction as well as in agriculture and food processing - often receiving very little pay.