I've had similar with my XP, only he had his girlfriends full support. Various different allegations were made to social services, ranging from neglect to sexual abuse.
At one point, I had social workers round every week with a new allegation.
My XP did whatever he could, regardless of the consequences to have DD removed from my care.
Solicitor told me that making allegations to social services is not seen as harrassment, no matter how often or how many are unsubstantiated.
What annoys me as well is that it is my DD who has this all on record...she will have these allegations next to her name, following her around for years, into adulthood. XP didn't care a jot about that.
It seems absurd to me that someone can make numerous unfounded and unsubstantiated allegations to social services, and yet never get told to stop.
I don't have an answer. XP is currently single, so not trying to impress the latest girlfriend of what a vile specimen I am, and he has no one to make out what a victim he is to gain sympathy and brownie points.
All XP ever wanted was to punish me for finishing the relationship, and he uses DD to do that.
Sorry I don't have any answers...but I sympathise, although I appreciate that isn't much help to you. 