The surprising figure in the article is that 1 in 4 prostitutes work on the streets. Seems like a made up number.
I've had a look at some of the report (which is a publicly available document) as nobody else seems to have. It looks like the 1 in 4 figure was submitted by one body submitting evidence, but another said 3%. The truth may well lie somewhere between, but the newspaper has picked out the most sensational.
It is an interim report and it's based on "evidence" submitted to them by anybody that wants to, with no original research directed by the Committee as far as I can tell. It does though seem fairly balanced in its conclusions (I have not read it all) in particular:
"11.The sex buyer law is a fundamentally different legislative approach to prostitution from that which is currently in place in England and Wales. It is based on the premise that prostitution is morally wrong and should therefore be illegal, whereas at present the law makes no such moral judgement. We acknowledge that the intention of many supporters of the sex buyer law is to protect sex workers, especially women, from the harm, violence and exploitation that can occur in the sex industry, but we also note that the sex buyer law makes no attempt to discriminate between prostitution which occurs between two consenting adults, and that which involves exploitation. Much of the rhetoric also denies sex workers the opportunity to speak for themselves and to make their own choices."