At least 32 men were captured and enslaved by members of an Irish and British travelling community gang, an investigation by the BBC has established.
BBC reports the gangs target vulnerable men who may be homeless or have addiction problems. They are promised new jobs with good pay but are transported abroad where they are forced to work long days in labor intensive jobs such as tarmacking or paving driveways for little to no money.
The investigation by BBC Ten O'Clock News and Radio 5 Live Breakfast confirmed cases in six European countries, including Sweden, Norway and Belgium.
One of the men told the BBC he was sent to Sweden with two other Britons for what they thought was a new job. The three had been homeless when they were picked up by a gang.
“I've seen people threatened with pickaxes. I've seen people kicked, punched. I've nearly been pushed off a moving vehicle. It's very tense. You're waiting for the next thing to happen, " the victim said.
The men were forced to work 14 hour days with little to no pay and lived in cramped conditions. They said they were frightened to escape before the Swedish police offered them help.
Last year a Swedish report into human trafficking discovered 26 incidents of non-sexual trafficking.
It stated: “In particular, these concern British and Irish tarmac and paving layers in Sweden.
“The victims do not usually report personally that they have been the subject of human trafficking because they often have no confidence in the authorities that administer justice and are afraid of acts of reprisal.”
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Cecilia Malmstrom, the European Commissioner for Home Affairs said she feared this was only the tip of the iceberg.
"It's a horrible crime and it's modern slavery," she says.
"They are using very vulnerable people and especially in hard economic times, people have lost work, nowhere to live, thrown out from families. We must act much stronger than we have done. It's only recently we have been aware of the amount of the problem."
David Ellero of Europol’s human trafficking agency says that there have been dozens of British victims.
"[They are] targeting the most vulnerable in society and forcing them to work, but the cases are not categorised as trafficking. The work is normally carried out in northern Europe, where they work in rural areas and focus on elderly victims.
"These people are intimidated into paying for substantial work, so it is a double crime, exploitation of the victims and fraud of the person paying."
Yvonne MacNamara, director of the Irish Traveller Movement in Britain, told the BBC her organization condemned "absolutely slavery and forced labor, not least because travelling people have been subjected to slavery and forced labor throughout their history, including recent history.
"If individuals are suspected of criminality, they should be subjected to the full force of due process and the law,” she concluded.
Click here to watch a special BBC video report on the investigation.