-consenting adults should not be told what they can and can't do with their own bodies in their own privacy
-prostitution has been around for a very long time in every part of the world. It is not called "the world's oldest profession" for nothing. Love it or hate it is is here to stay for a long time to come.
-prostitution can be a valuable outlet for clients who find it difficult to find sex otherwise because they may be disabled, unattractive or socially inept. Prostitution can also be an outlet for clients who just want sex without the difficulties or hassle that may come with a one night stand or a relationship.
-prohibition doesn't always work (have laws stopped people smoking weed? Have laws stopped people downloading copyrighted music from the internet?)
-prostitution is going to happen anyway legal or not, criminalization of a product/service leads to it being pushed underground
-UK prisons are overcrowded and we do not need to clog up the system sentencing adults who engaged in consensual sex. We should be looking at ways to keep people out of prison, not put more people in prison.
-criminalization will lead to more stigma therefore sex workers could be respected even less
-Sex workers and clients will be less likely to be regularly tested for STIs if it is illegal
-A law criminalizing prostitution will not prevent prostitutes from being assaulted or murdered. If someone does not care about the consequences of murder he is obviously not going to care about the consequences of breaking any other law.
-prostitution is possibly safer now than it has been in the past thanks to the internet. Sex workers can "screen" clients who make a booking and can make the choice on whether to accept the booking. There are feedback systems and forums used to warn sex workers about abusive clients to avoid.
-statistics on trafficking can be inaccurate and even intentionally exaggerated:
www.guardian.co.uk/uk/2009/oct/20/trafficking-numbers-women-exaggerated
-Noone knows the prostition industry better than prostitutes themselves, yet prostitutes are often not listened to when it comes to changing laws on prostutition. Some politicians seem to believe they are qualified to speak on behalf of sex workers.
-Some people argue the "Swedish model" criminalizing clients only is the best solution. Please have a look at the link below which has taken Swedish sex workers' opinions into consideration:
www.petraostergren.com/pages.aspx?r_id=40716
-Here is an article by Swedish media which initially suggests the law has been a "success" before suggesting prostitution has simply moved off the streets and onto the internet:
www.thelocal.se/27580/20100703/
-Despite the swedish laws (and over 10 years to enforce them), contact details for escorts in the captial Stockholm can be easily found by a quick Google search. This suggests it just isn't possible to censor the internet and prevent sex workers from advertising.
-An interesting and recent report here by United Nations-backed Global Commission on HIV and the Law (there is a section on prostitution including the "Swedish model"):
www.hivlawcommission.org/resources/report/FinalReport-Risks,Rights&Health-EN.pdf