Sex workers in brothels and saunas are being denied access to their passports and forced to work against their will, according to South Yorkshire Police.
In a crackdown on modern slavery across the county, police chiefs hope that raising awareness to the issue of sexual exploitation will result in more members of the public coming forward to raise their concerns.
Detective Sergeant Nikki Leach, who runs South Yorkshire's Anti-Slavery Unit, said: “Sexual exploitation is one form of modern slavery which is most prevalent for us across South Yorkshire.
“Typically, victims tend to be women and girls from Eastern European countries, who have either been trafficked into the country or asked to come over on false pretences.
“Like many forms of modern slavery, they are often promised a better life, money and a nice place to live. However sadly, that’s not always the case and they are then often controlled through violence and abuse, forced to work in the sex industry.
“From developing the intelligence picture of modern slavery across the county, we know that a significant percentage of people working in Sheffield’s sex establishments - such as brothels and saunas - do not have access to their passports.
“These people may not realise that they have been trafficked into the country, or that they are a victim of modern slavery. They may not know where to get help from or feel as though they can get help.
“This is why we need you to help us build up intelligence and gather information in relation to modern slavery and sexual exploitation."
She is urging members of the public to be alert to possible signs that victims are being sexually exploited.
“There are a number of signs you can look out for in relation to whether a house is being used a brothel," she said.
“There may be a number of women living there, but the house itself has very little furnishings or doesn’t look as though anyone actually lives there. There may be a large number of men coming and going from the address at all times of the day, along with vehicles.
"What I’d ask, is that if you see anything that causes you concern, to please get in touch with us.
“Together, we can build a better intelligence picture of incidents of modern slavery happening across South Yorkshire so that can protect vulnerable people and remove them from these horrendous situations.”
Call South Yorkshire Police on 101, Crimestoppers on 0800 555111or the National Modern Slavery Helpline on 08000 121700 to raise concerns.