If alcohol was suddenly discovered then (assuming it wasn’t immediately banned) it would almost be certainly be taxed at a uniform rate depending on the amount of the alcohol in the drink. However, in practice we have a confusing and somewhat inconsistent system of alcohol duties, with different regimes applying to cider, beer, wine, and spirits, and some drinks taxed at a flat rate while others are pro rata to the alcohol content.
There is some point to this, though, as broadly speaking weaker drinks are taxed less heavily than stronger ones, Partly this is to reflect the higher production and distribution costs and also, as I said here, while it is invidious to claim that one form of alcohol is “better” than another, it is less like hard work to abuse spirits and therefore there is a case for the tax system sending a message that they need to be treated with a certain amount of respect. It’s important to remember that Hogarth contrasted the squalor of Gin Lane with the prosperity of Beer Street – the former was certainly not making a general point about the evils of drink
This is a distinction that will be seriously undermined by minimum pricing, as pointed out in this blog post by Damian McBride which was mentioned by Phil of Oh Good Ale. Yes, it is that Damian McBride, Gordon Brown’s disgraced spin doctor, but he does have a background of working in the Treasury on alcohol duties and on this subject does seem to have some idea what he is talking about. Under minimum pricing, at the lower end of the market all drinks will sell at the same price per unit of alcohol, regardless of duty, thus giving a relative boost to spirits at the expense of beer and cider, maybe not quite what the anti-drink lobby are hoping to achieve.
(He’s wrong about Buckfast though – my understanding is that it generally retails for well above 45p/unit anyway, and its main appeal is not so much cheapness as its high caffeine content).
McBride makes another good point here that minimum pricing would in practice be difficult to enforce and would tend to favour the outlets that are often least controlled and responsibly run, namely small corner shops, again not perhaps the consequence sought by the anti-drink lobby.