eat the rich!
take one bite and spit out the rest!
Sorry, couldn't resist the aerosmith. I believe there is some merit in taxing everyone to a degree. It's the other side of the principle of no taxation without representation. If the people who demand and spend taxes should be accountable to the electorate, then the electorate, as a society should all be contributing. It's along the lines of 'buying' a stake in the country. Poor countries with despotic leaders tend to have large numbers of untaxed people. It's a lever for the despot to increase his power: leave the peasants largely alone so that at worst they are ambivalent to you no matter what crimes you commit against humanity elsewhere. If the government doesn't tax you, why get involved in the government or politics?
However, since nearly everyone in the UK pays some amount of VAT (even if just enough so that suspicion in the tax office is not aroused) and whatever other hidden taxes, it is unfair to tax people's income at 20% from £6000-odd. Even 10% would be too much in my proposal for broader income taxation. 5% or less might be a starting point.
Anyway: note that government ministers are paid less than £150000pa and hence should be under the 50% radar. Expect if ministers' pay goes up they will increase the threshold pretty sharpish. don't forget capital gains is still at 18% for the time being. I suspect to keep the rich from flocking away immediately and to artificially inflate the stock market by 'encouraging' high earners to take a reduced salary, but take the rest in options/investments.
Finally, whilst I have shown I'm not a flat-taxer, politicians and ultra-progressives tend to forget that the rich do pay more tax when they earn more money. 40% of lots is very much more than 20% of a little. Ah, socialism, and making everyone equally poor.