Sounds bad from the title, but it's not what you think.

My wife and I have an 18 month old boy, who's taken to slapping and smacking everyone. At first we just thought it was phase he was going through, but it's continued. At first when he smacked us we would make him give us a kiss and a hug to say sorry, but we soon realised that by allowing him to kiss and hug us it was kind of making it a reward for smacking, because as soon as he did it he would go straight for a kiss and a hug, so we stopped that. We have tried ignoring him for a while, which seemed to work for a bit, but now not giving him attention makes him go for longer.

It's now got to the point where it can be embarrising to take him out as he can randomly walk up and slap other kids, then if we shout at him in front of people we get the frowned brows from the other parents, if we say nothing we also get the frowned brows, so were damned if we do and damned if we don't.

Does anyone have any suggestions as to what we can do to stop him acting like this.

BTW he's actually a really cute child, not bad tempered or selfish, he just has a tendency to slap people

So you get some frowns, I guess when I went over and slightly slaped his hands I would get boos

Time out, a raised voice all work and some never work,

He needs to know that hitting you and his mom isn't right. You can try buying a chair, for him to sit in, and call it the naughty chair. Whenever he hit either one of you make him sit in chair and tell him why he is going to the chair. If he gets out the chair before his time is up, go and get him and put him back in the chair and whatever you do don't let him get up until his time is up. You can even buy and timer so he knows when his time is up. This worked for my nephew.

Or you can take his toys away but that might or might not work because of his age. When my daughter was that age and starting hitting people for no reason I used to give her pow pow on her hand and tell her about hitting and why I didn't like it and that worked for me because she didn't like getting hit on her hand.

Whatever you do stick with it and be firm and both parents need to do it and work together. He need to know that hitting is bad and he'll get punish. Maybe someone else will come along with more suggestions but I hope this helps.

He needs to know that hitting you and his mom isn't right. You can try buying a chair, for him to sit in, and call it the naughty chair. Whenever he hit either one of you make him sit in chair and tell him why he is going to the chair. If he gets out the chair before his time is up, go and get him and put him back in the chair and whatever you do don't let him get up until his time is up. You can even buy and timer so he knows when his time is up. This worked for my nephew.

Or you can take his toys away but that might or might not work because of his age. When my daughter was that age and starting hitting people for no reason I used to give her pow pow on her hand and tell her about hitting and why I didn't like it and that worked for me because she didn't like getting hit on her hand.

Whatever you do stick with it and be firm and both parents need to do it and work together. He need to know that hitting is bad and he'll get punish. Maybe someone else will come along with more suggestions but I hope this helps.

We have tried the naughty corner, but I think he actually thought it was a game as he would often walk over to it and sit in it himself. My wife and I looked at each other and resisted the temptation to laugh out loud.

Have taken the toys away, this creates plenty of tears for a bit.

We are pretty firm with him and do work together but not a great deal seems to be working at this stage

We don't want to resort to slapping him as we don't see this as being the right way to manage his behavior

At 18 month's do children have the mental capacity to distinguish right from wrong, this is our first child so we have no idea.

I think kids are smarter than their given credit for but at his age he will test you a lot to see what he could get away with and at this age he can be taught between right and wrong. At this age I taught my daughter that with every action, there would be a reaction, whether it be a time out or pow pow on her hand for bad behavior, or a big hug and kiss for good behavior.
I've to go now because my baby is waking up but will come back to finish answering your question.

I think if you give him a time out it would solve the positive attention problem

From what I know most people recommend the time out be about half the child's age and with a timer (preferably he can't reach).

For the he treats it like a game... Tell him no toys or play till he takes his time out or take things away if he gets up for example "If you don't get back in the corner no tv time")