The Sunday Times today has a full page feature on 'Our tax manifesto: what Brown could do to help.' Now, admittedly, this was probably put together by the journalist in a very tight time frame.
However, suggestion three is 'bring back mortgage relief'. It took a big struggle to get Mrs Thatcher to reduce what was originally brought in a subsidy to counteract an unpopular tax that used to be applied to property owners (Schedule A as I remember). Labour finally got rid of the relief (Schedule A went after it cost the Conservatives at the Orpington by-election).
It is argued in the piece that it could be limited to first time buyers. In practice, actually ensuring someone was a 'first time buyer' would take a lot of time and effort, involve endless complications and be open to fraud.
The most basic objection is that this involves subsidising an investment that should yield positive returns in the longer run. So those in social housing or in private lets would be transferring some of their taxes to those making house purchases.
From various hints the Government seems to thinking of using the tax credit system and the winter fuel allowance to distribute its fiscal stimulus. But not everyone who is entitled applies for tax credits, while neither measure would reach those who are in work but not well paid and without children.
Far better to increase personal allowances and make an offsetting change in the higher rate threshhold.