We had a similar situation with our 3 1/2 year old daughter. She was having accidents daily. When I stopped to take a closer look it was clear that we were in fact in a power struggle with her. In our case I believe it was lack of positive reinforcement for good behavior. I made her a sticker reward "potty champion" chart and gave her lots of praise when she chose to go to the bathroom instead of having "accidents". In less than two days she was not wetting her pants anymore. It has been about a month and I think she has only had one accident (which I believe was from waiting too long to go and not just choosing to potty her pants like she had previously been doing). I would recommend that you take a closer look at other things going on. It very well could be stress related. I would try not to give it too much anger attention, this would just create more stress. I agree with others that he should have to help clean up the mess but not in a serious punishment sort of way, more like "oh, what a bummer, look at this mess you made. When we choose to make messes, we have to clean them up".
Good luck!! It was very stressful for us until we realized that this seemed to be the only thing she felt she had any control over. Kids need to feel like they have some control over their lives. If we don't give it to them (in a positive guided way) they will resort to extremes to take it!