The NCA said the growth in modern slavery was being driven by global gangs increasingly recognising the amount of money they could make by controlling people within a huge range of economic sectors, rather than just dealing drugs.
"But what we do know though is that the information and tools we now use to disrupt these gangs and identify offenders we are going to need after Brexit as well".
"The growing body of evidence we are collecting points to the scale being far larger than anyone previously thought". But Will Kerr, the NCA's Director of Vulnerabilities, said the downside of Brexit could be that it might be harder to co-operate with European law enforcement agencies.
He said that the problems authorities faced were further complicated by the fact some people do not realise they were a victim of slavery. "This should not be acceptable in any way, shape or form".
A surge in operational activity focusing on labour and sexual exploitation co-ordinated by the NCA through May and June - codenamed Operation Aidant -led to 111 arrests in the United Kingdom and some 130 people being encountered who may be considered as victims.
"We continue to support the work of the National Crime Agency to leave criminal networks of traffickers and slavers nowhere to hide".More news: 'Bombastic comments' over North Korea not helpful, warns United States defence expert
Diane Abbott, the shadow home secretary from the Labour Party, commenting on the report issued by the NCA, stated that the criticism of the agency's inability to tackle human trafficking raised serious concerns.
Instead, they are sold into prostitution, or paid a pittance to work in farming, construction, food processing, vehicle washes or even harvest cannabis.
They explain that signs of abuse include visible injuries, a distressed appearance and any indication they are being controlled by another person.
Others sold into slavery could be kept in pop-up brothels, where sex workers promised a better life are left penniless with few clothes other than underwear, while some can be working at cannabis factories, he said.
The agency estimated that there were tens of thousands of victims.
Kerr said that as well as prostitution, people are being trafficked to work in a number of industries, with the most high risk including fisheries and the maritime industry, agriculture and construction, and food manufacturing and processing.More news: Harsh Rhetoric Between North Korea and Trump Worries Investors
"The scale and scope of this problem has shocked us", Kerr said, as he announced a national campaign aimed at encouraging members of the public to report any suspicious activity.
Mr Kerr cited the case of a 12-year-old Roma girl stopped at border control, bound for a life as a domestic slave after she was "effectively sold by her father".
She was living with a family and was expected to walk their children to school every day, and then spend the rest of the day cleaning the house, receiving no education herself.
Although victims from 109 different countries have been identified, many come from Eastern Europe, Nigera or Vietnam, and British criminals make up a high proportion of offenders, who are not discerning in the nationalities of victims that they exploit. "Twelve years old, same age as my youngest son".
The PSNI created its human trafficking unit early in 2015, a move Mr Kerr says put them "ahead of the curve".
Anyone with information about possible slavery gangs can contact the NCA on 08000 121 700.More news: Paula Creamer gets Solheim call-up after Korda withdrawl
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