I don't think it can.
Apart from Ian Bone and his 'Bash the Rich' loonies, there is surely no conceivable way that this can be seen as morally acceptable?
I mean, £63.8%?! After all, £150,00 (which is the high earner threshold) isn't *that* much.
And of course, it has a worrying knock-on effect. At the moment, the Government are using taxpayers' money to prop-up dying (or at least struggling) industries - the car industry for example. And they are paying for this by squeezing the productive side of our economy.
So you penalise the good to pay the bad and after not too long, the good get annoyed and go somewhere else. It does little more than reward failure and kill aspiration.
Yes? No? Maybe?