Parenting suggestions plz.

How do you girls co parent and disipline your kids?? I had never touch my kids but when they do something wrong I do tell them I will spank them but i will never lay hands on my kids. My son got brand new shows and he destroyed them the 2nd day. I bougth him a new pair again and told him if he dirty them again he will get spank, I'm not with his father but I am in a relationship with a guy that does everything for my kids and took them in at 2 &3 they are about to turn 5&6 in couple of days. Well my son told his father we spank them from what my kids father stated. He tried to turn my son story to saying we actually spank him. What can I do because it's not true and it just cause such a big problem when my kids where dropped off back home father only gets my kids 3 times of the month. He has no idea or anything about my kids life such as only the day he see them 1st sat 2nd & 3rd day of every month.