Ignoring references to personal experiences of poor workplace conditions, as someone mentioned above, the Scarlet Alliance is an association which supports sex workers. In terms of official government agencies dealing with these issues, I imagine there would only be something to generally manage workplace issues (there's no body dealing specifically with the sex industry much like there is not one dealing specifically with people in medicine). It has to be said though that anyone not officially employed (e.g. working for cash in hand) might have some difficulty bringing up their case.

There must be some kind of group which gathers information on the sex industry in order to implement policy, but that's not what you're asking about (nor do I think such a group would be in operation all the time).