This 1/2% tax on homes is basically updated Georgist economics.  Henry George was the most influential proponent of the land value tax, an idea that has floated around in liberal circles for two centuries. The problem is that implementing the tax would immediately discount the price of your home. Not the smartest thing to do in an era when many are struggling to stay out of negative equity.  A middle-class family home in London valued at £2,000,000 would lose £100,000 (1/2% x £1,000,000 x 20 multiple). Douglas McWilliams, chief executive of the Centre for Economics and Business Research, points out that it would hit the property market hard, because prices well below the £1 million level would be knocked as well:

… home owners would face a double whammy – more tax and a cut in their wealth. The tax would add to Council Tax and Stamp Duty as yet another heavy tax on homeowners. It would be regionally unfair, since virtually the entire tax would be raised in London and the South East, and would be very unlikely to raise the £1 billion the Lib Dems expect – more like £600 million on  our calculations. Unfortunately the current crisis is not a time for clever-clever ideas for screwing additional tax out of the already hard pressed middle classes at a time when property prices have already fallen sharply, the top rate of tax has been raised and the tax deductibility of pensions has been largely removed.

“Vote LibDem for more negative equity” hardly seems like a winning slogan…

UPDATE : They seem pretty intent on shooting themselves in the foot with this extra tax on homeowners in the South East, it will be a gift to Tory candidates in LibDem seats.  It certainly won’t go down well in leafy Twickenham. Vince Cable has a majority below 10,000…