Meacher's argument is simply b.s. (http://www.guardian.co.uk/commentisfree/2012/may/31/how-to-kickstart-uk-economy)
he says
"In the short term, the most feasible approach is to impose a capital gains tax charge at the current rate of 28% on the topmost layers of wealth, the £155bn gains amassed by the 0.003% over the last three years"
The 0.003% he's talking about are the richest 1,000 in the population and the £155bn gain the claimed increased (by the Sunday Times, not HMRC) in their wealth since 2008.
But, there's no "capital gain" as we know the term today - i.e. when selling an asset that attracts CGT.
I'm sure all (or nearly all) of these 1,000 people have businesses. It's the value of the businesses that have increased since the low point in 2008.
On what grounds is he going to say to these 1,000 business "based on no current law - but maybe a retrospective one I've just made up - please give me 28% of the increase in the value of your business since my arbitrary starting low point of 2008" ?
Where would they get the 28% from ? Sell shares, crashing the value of 1,000 firms ? Would cause a massive backlash against the UK from businesses, government having no respect for the law.
Plus, it would never work. Before they could get the law passed, the businesses would relocate their head offices abroad (rightly so) and avoid this.