I don't understand this "taking their passports away". It's not like you're a slave if you lost your passport. Also, you can travel pretty much everywhere within Western Europe without a passport, it's called the Schengen zone.
Also, you do realize that you still need your passport for identification for basically anything right? Living in Germany, the first thing you always hear when visiting any institution, police, hospital, pharmacy, etc. is 'Ausweis bitte!'. Without an ID, you will not be served unless you're in a life threatening emergency.
And the girls would be too afraid to go to the authorities for help, for the fear of beatings or the pimp gangs taking revenge out on their families back home, since they knew where they lived.
In which western European countries are human trafficked girls afraid of going to the police? It's hard to imagine any western European country where authorities wouldn't take this extremely seriously, and where this wouldn't be front page news.
Spesifically in UK there was a scandal with local police basically ignoring the issue.
The girls are seen as illegal immigrants first, and any kind of victim second. Then there is the risk of blackmail, as in, if the girl's concervative family find out that she has been a sex slave, she would be disowned.
If none of the above issues apply, it is also important how the girls think the police will react, rather than how they will actually react.
And lastly, without your passport you are mostly stuck in an unfamiliar country, don't speak the language and probably you have no money either.
it is basically slavery.
Source?
> without your passport you are mostly stuck in an unfamiliar country
Without your passport you just go to your country's embassy and get a new one. Or if that's not possible because your country doesn't have them, claim refugee status.
[0] https://en.m.wikipedia.org/wiki/Home_Office_hostile_environm...