What legal action can I take against the other parent slandering me to my child?

I have a 14 yr. old daughter who lives with her mother and the mother constantly slanders me and my wife to my daughter to the point that now my child has begun to hate us and believe what her mother says. I have set guidelines multiple times to my ex about her hateful talk and she has ignored it every time. I know in our divorce papers it says neither one of the parents can slander the other to the child but what legal action can I take? My child is now refusing to see me and has begun cussing me like her mom does and I want it to stop before my child's heart is completely corrupted by her moms hate.