There is no such thing as the worst gang because they're all pretty bad. It is very difficult to classify them in terms of who is worse than the other because they all have pretty bad things associated with them.
Ross KempSome bosses believe they can't afford to employ someone legitimately - so they employ them illegally.
Ross KempPeople-trafficking is modern day slavery. There are more slaves today than there were at the height of the slave trade.
Ross Kemp