Take a look at this article in The Herald. Notice anything? I noticed the headline is a lie. It reads "Aberdeen police claim new sex laws increase prostitution" but the article explains that police believe the change in the law has moved existing prostitution to different areas. The "increase" comes from the BBC who report that there has been an increase in the number of arrests. But surely tightening the law means you would expect more arrests. So it would seem the law is doing exactly what it is supposed to do. And the more you arrest, the less are left on the streets? No?
The law change was supposed to crack down on the men who visit prostitutes, the idea being weirdly that this is in some way "fair" to legally pursue both parties. This of course misses the point that the vast majority of prostitutes are not doing the job out of free and straightforward choice. It makes sense to criminalise those who use prostitutes because it reduces demand and thus the incentives to those who would force women into this role. It would make more sense however to simultaneously decriminalise the women themselves, so that they can seek help and a route out of prostitution when they are ready and feel able to.