My daughter’s ex refuses to pay for his child

My daughter has seven year old child and the father has stated quite bluntly that he is paying nothing towards his child.

She contacted the CSA several months ago and because she did not have his address and place of work they could not do anything to enforce maintenanc payments for his child What can she do as the CSA choose to ignore her cry for help she is asingle girl trying to do the right thing for her son.

The father turns up now and again to see his child and the child becomes very emotional and confused as to what is going on My ex-partner has a new partner and is engaged to be married shortly leaving all his parental reponsabilities behind hoping they will go away.

HELP PLEASE!