A Home Office report, published on Monday this week, estimated that the average cost of a modern slavery case is £330,000, including loss of support, lost earnings and law enforcement.
By comparison, the total expenditure to counter modern slavery by law enforcement agencies across government was around £83.5m in England in Wales in 2015-16, according to the Office for Security and Counter-Terrorism.
The Home Office said there are between 10,000 and 13,000 victims of modern slavery in the UK, which means the total estimated cost varies between £3.3bn and £4.3bn.
The government will now hold an independent review of the Modern Slavery Act 2015, to ensure that it is effective in dealing with the crime.
The review will be led by MPs Frank Field and Maria Miller as well as Baroness Butler-Sloss.
Victoria Atkins, minister for crime, safeguarding and vulnerability, said: “This awful crime is evolving, it is our responsibility as citizens, businesses and governments to do all we can to stop exploitation.
“This independent review will help us identify what more we can do to tackle this terrible, global injustice by enhancing the Modern Slavery Act where necessary.”
The legislation currently requires every business with an annual turnover of £36m and over to publish a statement on its website outlining what it is doing to prevent and tackle modern slavery in its operations and supply chain.
Butler-Sloss said: “The Modern Slavery Act is a splendid piece of legislation but it is very important to review how well it is being implemented and how it could be improved.”
According to the act, a person commits modern slavery when they “hold another person in slavery or servitude and the circumstances are such that the person knows or ought to know that the other person is held in slavery or servitude” and when a person is forced to perform “compulsory labour”.
Alongside the review, the government announced it will invest £2m extra into the Independent Child Trafficking Advocates scheme, which works with trafficked children.
