At least seven police forces in England have not charged a single person under modern slavery legislation introduced more than two years ago.

The Modern Slavery Act was put in place in May 2015 to make prosecution easier and help protect victims. But despite a rising number of reports under the act, several police forces have not charged anyone while others have done so only in one or two cases.

Data from two thirds of police forces obtained through freedom of information legislation shows that across England and Wales the number of reports under the act rose from 469 in the financial year to 31 March 2016 to 1,214 in the same period a year later and 1,042 in the eight months to November 2017.

But during this period the total number of charges declined, from 94 to 43, with 4.13% of cases leading to formal action in 2017 – down from 7.58% the year before.

Modern Slavery Act gives UK companies a free pass to profit from slavery overseas Read more

Thames Valley police is one of seven forces that laid no charges, despite receiving 203 reported cases under the Modern Slavery Act from April 2015 to November 2017. Dorset police, which only supplied figures up to October 2017, laid no charges but received 45 reports. The other forces that did not bring cases were North Yorkshire, Cumbria, Devon and Cornwall, Dyfed-Powys and Norfolk.

Charities and politicians have expressed concern, although they noted bringing charges is complicated as witnesses often withdraw from proceedings. Forces could also be bringing charges under different offences, such as conspiracy or rape.

Jakub Sobik, from Anti-Slavery International, said the number of charges was a reflection of shortcomings of the government’s response to the issue. “The main point of the Modern Slavery Act was to make prosecution simpler, so if the number of charges under it aren’t growing, that’s concerning,” he said.

The Crown Prosecution Service said: “Charges can be brought under a variety of legislation, including the Modern Slavery Act 2015, the Sexual Offences Act 2003, the Asylum and Immigration Act 2004 and others. In 2016-17, we received 271 referrals from police and charged just under 70% of those cases, a charge rate only slightly below the national average for all crimes.

Quick guide Modern slavery Show Hide What is modern slavery? About 150 years after most countries banned slavery – Brazil was the last to abolish its participation in the transatlantic slave trade, in 1888 – millions of men, women and children are still enslaved. Contemporary slavery takes many forms, from women forced into prostitution, to child slavery in agriculture supply chains or whole families working for nothing to pay off generational debts. Slavery thrives on every continent and in almost every country. Forced labour, people trafficking, debt bondage and child marriage are all forms of modern-day slavery that affect the world's most vulnerable people.

How many people are enslaved across the world? The UN's International Labour Organisation (ILO) estimates that about 21 million people are in forced labour at any point in time. The ILO says this estimate includes trafficking and other forms of modern slavery. They calculate that 90% of the 21 million are exploited by individuals or companies, while 10% are forced to work by the state, rebel military groups, or in prisons under conditions that violate ILO standards. Sexual exploitation accounts for 22% of slaves. Where does slavery exist? Slavery exists in one form or another in every country. Asia accounts for more than half of the ILO's 21 million estimate. In terms of percentage of population, central and south-east Europe has the highest prevalence of forced labour, followed by Africa, the Middle East, Asia Pacific, Latin America and the Caribbean.

Who is profiting? In 2005, the ILO estimated that illegal profits from forced labour amounted to more than $44bn. The UN's global initiative to fight trafficking says people trafficking is the third-largest global criminal industry (pdf) behind drugs and arms trafficking. The ILO estimates that people in forced labour lose at least $21bn each year in unpaid wages and recruitment fees. Slavery also exists within global supply chains, generating huge profits for those who control this industry in free labour.

“These crimes are some of the most complex handled by the CPS, but we work closely with investigators to build robust cases, while ensuring victims are protected.”

Thames Valley police said: “Frequently, cases of modern slavery require further evidence in order to bring an offender to justice.”

Kent police recorded nine charges out of 280 reports over that period. West Midlands police had 547, the highest number of reports, leading to nine charges. Some forces said cases were still under investigation.

Supt Andy Waldie, from the Kent and Essex serious crime directorate, said: “The absence of a criminal charge does not mean a victim has gone unsupported or indicate a lack of enforcement action, as offenders may be charged with associated offences, such as assault.”

Other forces noted that getting victims to confront perpetrators was a big challenge.

The MP David Lammy said: “This legislation is absolutely crucial to tackling trafficking, but also in cracking down on organised crime and criminal gangs. Knife crime, for example, is not being driven by minors but by the gangsters and kingpins who are trafficking drugs ... If we want to get to grips with serious, organised crime and the people who perpetrate it then the Modern Slavery Act must -absolutely be used to its fullest.”

The Home Office said: “We are now seeing the first convictions for the new offences prosecuted under the Modern Slavery Act. These are often highly complex cases ... Given the significant increase in operational activity directed against modern slavery over recent months, we expect to see more prosecutions commenced as investigations reach the point of charge.”