There could be 10-13,000 victims of slavery in the UK, far more than previous estimates, analysis for the Home Office suggests.
Modern slavery victims are said to include women forced into prostitution, “imprisoned” domestic staff and workers in fields, factories and fishing boats.
The figure for 2013 is the first time the government has made an official estimate of the scale of the problem.
The Home Office has launched a strategy to help tackle slavery.
It says the victims include people trafficked from more than 100 countries – the most prevalent being Albania, Nigeria, Vietnam and Romania – as well as British-born adults and children.
Data from the National Crime Agency’s Human Trafficking Centre last year put the number of slavery victims in the UK at 2,744.
The assessment was collated from sources including police, the UK Border Force, charities and the Gangmasters Licensing Authority.
The Home Office says it used established statistical methodology and models from other public policy contexts to estimate a “dark figure” that may not have come to the NCA attention. The Home Office said the “tentative conclusions” of its analysis is that the number of victims is higher than thought.
The Modern Slavery Bill going through Parliament aims provide courts in England and Wales with new powers to protect people who are trafficked into the countries and held against their will. Scotland and Northern Ireland are planning similar measures.
But outlining the strategy for government departments, its agencies and partners, Home Secretary Theresa May said legislation is “only part of the answer”.
The “grim reality” is that slavery still exists in towns, cities and the countryside across the world, including the UK, she said.
“The time has come for concerted, co-ordinated action. Working with a wide-range of partners, we must step up the fight against modern slavery in this country, and internationally, to put an end to the misery suffered by innocent people around the world.”
The Home Office says the UK Border Force will roll out specialist trafficking teams at major ports and airports to spot potential victims, and the legal framework will be strengthened for confiscating the proceeds of crime.
The modern slavery strategy will also see:
• The government identify “priority countries” to work with, as well as other organisations including churches
• British embassies and high commissions and NCA liaison officers develop local initiatives abroad
• Work to strengthen the response by local authorities to child abuse, including trafficking
• Work to raise awareness among homeless shelter staff of the signs of modern slavery