There are several diets that allow alcohol in moderation. For example, the Slow-Carb Diet allows 2 small glasses of red wine where small = 125ml and the Sirtfood diet also encourages the use of wine because it is a Sirtfood.
But the problem with consuming alcohol on a diet is that it is a domino food, i.e. it is very easy to have another and then another again. Nuts and crisps are very similar in this regard.
This year I have started dieting again aggressively after a year of carelessness. I am following the Slow-Carb diet - more or less as I am allowing myself some cheese occasionally.
Since January the weight has been disappearing, but a few weeks ago I hit a problem - the fat started to come back. A little analysis in the recycling bin showed a few too many wine bottles. For the last two weeks, I have significantly cut my alcohol consumption. You can see the problems starting on 5/3 and me getting back on in the last 2 weeks simply by cutting down on booze.
My advice: even if the diets allow it, give yourself a break for a couple of weeks. And by this, I do not mean abstain - have a day off a week, but in general cut it out until the weight has started to shift.
Now the trained observer will notice from this blog that I brew and drink beer. I should point out that my beer drinking is restricted to 52 days a year - Saturdays. The Slow-Carb diet allows a day a week of cheating. I also take a break on holidays. The drinking I'm really referring to here is the allowed drinking on the diets, but I would give yourself a break of a month from all of it particularly when you start a diet.