Crimestoppers today highlighted the way these brothels can be used to house women against their will, with many suffering abuse in the most inhumane conditions.
It said the brothels are usually newly-acquired properties in towns and cities, which may only be used as a brothel for a short period of time.
They are often privately rented flats or houses, but budget hotels or holiday properties are also sometimes used.
Gemma Wilson, Yorkshire and Humber Regional Manager for Crimestoppers, said: “These brothels are dens for criminals to recruit and house vulnerable women who are then put through ordeals no woman should have to go through.
“People who run these brothels run them within our communities, think they can get away with it, and have no limits as to what they will do to their victims."
The independent crime charity said many of the women forced to work in these brothels are Eastern European, Thai and Nigerian; and may also be living in the property for the short period of time the brothel is running.
Its campaign includes teaching people about the signs to look out for in their own neighbourhood, such as a number of women living at the address, frequent male visitors who do not stay for a long time and multiple vehicles visiting a property.
Ms Wilson said: “On the victim’s behalf and that of Crimestoppers, I’m appealing to people who might have information on those running these brothels, so we can shut them down and give the victims some hope of getting their lives back.”
Earlier this year, the head of West Yorkshire’s dedicated human trafficking unit said one of the fears was that some of those forced into sex work are reluctant to co-operate with authorities because they are still earning more than they would have done in their home countries.
Detective Chief Inspector Warren Stevenson said: “You have this issue that they are prepared to do it, they believe there is nothing wrong in it, they have been brought into this, and they have an element of freedom about their movement, which causes some issues for the investigation.
“But it is all do-able, we have just got to understand how to investigate, prove it, and protect them, and educate them that they are victims of human trafficking, rather than criminalising them.”
The focus is largely on those behind the trafficking of women such as David Zielinski, a key member of a slavery gang operating in Bradford who was made the subject of a 10 year slavery trafficking prevention order.
West Yorkshire's unit has also secured the co-operation of authorities in Poland to the orders in their home country after their prison term ends.
What are the signs to look out for?
Limited activities usually associated with new people moving into a property (e.g. no removals)
Limited, or scarcely, furnished, appears no one actually living there
Multiple women living at the address, or who may be brought to and taken from the address by an individual
Multiple vehicles visiting the property at any one time
Many frequent visitors, usually male, who don’t stay for long periods of time.
If you have any information on pop up brothels in Yorkshire and Humber, contact Crimestoppers anonymously on 0800 555 111 or visit the website here.