Bites!!

Hi everyone, just looking for a little bit of advice.

My 4yr old daughter has overnight contact with her father every other weekend. Over the last 6 months she has been coming home covered in bites (I suspect they are flea bites). I have asked her dad to try and do something to prevent it and he refuses. He says he has frontlined his cat and theres no issue. Quite clearly there is as she still comes home covered all the time. I have taken her to the GP and his advice is that he seekd help from a vet and if that doesn't work then environmental health should be brought in to find the source of the problem. Even with the GP's advice he still refuses to do anything. My daughter is abviously irrated by them all the time and is now scarred from them. I have asked for help from social services who refuse to get involved. I am currently refusing to let her go for overnight stays but agree to him seeing her in the daytime when he wants as long as he doesn't take her to his house. He is refusing to see her at all unless it is for overnight. He is now not seen her for 6 weeks. What more can I do, any help and advice would be really appreciated.