My Husband Wont Discipline Our Daughter!?

My mother used to have this problem with my step dad and my little half sister....he wouldnt do anything for her or me and my mom did everything...i remeber she used to unplug whatever he was on and told him to actually tech us something. I would say "hey honey im going to the store can you watch her?" every once in a while and see after a few times he might actually learn (my mom did this and it worked) Good Luc<333