In his relaunch interview  in today's Guardian, Nick Clegg calls for a new wealth tax, declaring that "if we want to remain cohesive and prosperous as a society" those of "very considerable" wealth should make an "extra contribution". To which Labour has replied: why did you vote to abolish the 50p tax rate, then? It's a reasonable debating point (the decision to scrap the 50p rate was both politically and fiscally foolish) but it's also rather disingenuous. As anyone who has read any of Clegg or Vince Cable's speeches will know, the Lib Dems have long argued that the burden of taxation should be shifted from income towards wealth (as, indeed, has the New Statesman ). There is nothing inconsistent in Clegg calling for a wealth tax while also supporting the reduction in the 50p rate to 45p. You could argue that new taxes on wealth should complement, rather than replace, those on high incomes (and you'd be right), but this shouldn't blind the left to the merits of Clegg's intervention.
In Britain, wealth is concentrated in even fewer hands than income and represents a huge untapped source of government revenue. If taxes on income are to be reduced, as they must be (if one includes National Insurance, the effective starting rate is 32%), either through a significantly higher personal allowance or through a reduction in the basic rate, then taxes on wealth should be increased. As Clegg states:
In addition to our standing policy on things like the mansion tax, is there a time-limited contribution you can ask in some way or another from people of considerable wealth so they feel they are making a contribution to the national effort? What we are embarked on is in some senses a longer economic war rather than a short economic battle.
Taking their cue from John Stuart Mill, the Lib Dems rightly argue that the tax system should do more to reward merit, enterprise and innovation. As Cable put it in his essay for the New Statesman on reclaiming Keynes , taxation should be diverted away from "profitable, productive investment" and towards "unproductive asset accumulation". Wealth taxes are harder to avoid than those on income and, as a recent OECD report  noted, they benefit the economy by shifting investment away from housing and into wealth-creating industries.
For now, Clegg's proposal raises more questions than it answers. Most obviously, at what rate and threshold would a wealth tax be set? But the details, we are promised, will be filled in by the time of the Lib Dem conference next month. What one can say with certainty is that, as Jonathan Portes  puts it, it is both "good economics and fiscally progressive" to sharply increases taxes on the wealthy. By all means assail Clegg for his support for the government's disastrous economic strategy and its punitive welfare cuts, but don't ignore the fact that the most creative thinking on taxation is taking place in his party.