The idea
OK, so I'm stretching the remit of this formula but this government is doing so well and looking likely to give us back our freedom and resisting the urges, and the opportunities, to impinge freedoms further. However it has also made, a very few, bad "noises" when it comes to liberty, probably provoked by the socialists.
Put up the tax if you must (although use this to either put down tax elsewhere or find more savings so as to keep the 20:80 ratio) but let's not have either minimum pricing or bans on selling below cost price.
Why is it important?
Minimum pricing, or bans on selling below cost price, will be difficult to enforce, they are illiberal and they will, through the basic actions of economics, impact on the price of all substitute goods and all substitutes or substitute etc. (especially where those substitute goods are sold by the same vendors).
To define "cost price" is also going to be difficult.
You don't have to be William Gladstone to understand that a government enforced cartel in the drinks industry is a very bad idea. It can only benefit the drinks industry, at the expense of consumers.