My wife and I have been together for five years and today my wife told me to spank the kids b13 g12 b11, to which I told her I was not comfortable doing that. I initiate punishment in the form of grounding or taking away things, that seems to no longer curb the undesired behavior and my wife wants me to escalate to physical punishment which I’m not comfortable doing and explained that to her. Her response was not very understanding and she became short with me and continued by stating she can’t do it be herself. I don’t know what to do. – Scott
Scott,
You’ve got it right. But there’s more involved than just the issue of spanking kids. Step-children in their teens are the most difficult age group for Stepdads to bond with. Spanking them will probably erase any positive connection you’ve been able to create with them. Single moms who become overwhelmed let their kids get out of control. When they get married these ladies often expect their new husband to take a heavy hand with the kids. They quickly find it’s a bad idea. It’s important to improve their behavior –but it’s vital to be strategic.
Don’t Be the Bad Guy
Establish that you will NOT play the punisher. Talk with your wife 
and come to an agreement about what punishments (if any) should be expected when the kids mess up. You need to share the responsibility of deciding on what’s acceptable, but she needs to be responsible for telling the kids what their punishment is. Naturally, you will support her in holding them to her expectations but you won’t have to be the bad guy. She has a bit more wiggle room than you do. If she’s heavy-handed the kids will eventually forgive her, but they’re likely to hold a grudge against you. It doesn’t take much to go from being the Stepdad to being the enemy. Don’t allow yourself to be put in that position.
Be Strategic
Spanking may seem like a natural way to take punishment to the next level but 
kids have a stronger emotional reaction to physical punishment than other forms. There are better ways -as you mentioned. With all of the great gadgets kids have nowadays you get a lot more traction by limiting their phone use or taking away their computer. Kids are addicted to their electronics, so this usually gets quick results. You can escalate this by taking the punishment up a notch if they aren’t responding. You can also modify their behavior by taking a privilege and making them change their behavior to earn it back. On top of that, if your wife plays the bad guy you can play the cop. Just say “Sorry, I don’t write the laws, I just have to enforce them.” They’ll be very motivated to get back the thing they lost. It’s better than spanking –and much more effective.
The Big Slam
Do you have a problem with your kids slamming their door to make a point? Learn how to remove it! Most doors have just three pins holding the hinges together. All you need is a hammer, 
a flat-head screwdriver and a couple of minutes to pop the door off. The loss of privacy will immediately get your teen’s attention. I got so good at this I could do it in about a minute. It became an on-going threat. “Do you want to lose your door?” When you take it off put the door in the garage or your room and let them know they can have it back in a week –faster if they change their attitude. This works very well. You can find a video that shows how to do this – here.
Partnership
A Stepdad and his wife need to work as a team raising the kids. Your presence is important. Kids with a full-time loving father do much better in life. Kids without a full-time male role model are more likely to drop out of high school, more likely to commit crimes, more likely to be teen parents and struggle in life as adults. Read more about those statistics here. Your role is important but it’s vital that you are united in the standards you set for your kids.
Agree on The Rules –and Stick to Them!
Talk about the rules and punishments then talk to the kids. Any time you
discuss punishment be sure the kids can’t hear you. If they know you’re the one taking a strong position they’ll start to paint you as a bad guy. Again –you need to be united when you’re in front of the kids. They will find the weak parent and manipulate them to get what they want. Some Stepdads are tempted to have a light touch with parenting because they want the kids to like them. Don’t do it. Kids will take advantage of your kindness. They will test you. It’s human nature to try to get what you want. If you and your wife work together they won’t be able to get around you. There can be no weak link.
You can read more about this subject here.