When politicians need an eye-catching initiative they end up heading for the hole in the wall. Tony Blair came up with the idea of getting the police to march yobs to cash machines to pay on-the-spot fines. And now the Coalition is recommending that the public be given the option of making charitable donations whenever they use a cash machine. The idea is likely to be included in a White Paper today, along with other suggestions, such as rounding up customers' bills in restaurants to the nearest pound and channelling the extra pennies to worthy causes.

David Cameron is also due to make a speech in Milton Keynes today in which he will propose an incentive system for volunteering based on supermarket loyalty cards.

Will any of this do any good? A recent poll for The Independent on Sunday found that the number of people who feel that they understand what is meant by the words "Big Society" has gone down. That is what is behind today's flurry of political salesmanship for the idea. But the problem with the Big Society agenda is less public recognition than public cuts.

The scale of spending reductions being forced on local councils is already undermining third-sector organisations and charities which rely on local authorities for part of their funding. And these are the very bodies that the Government says should play a greater role in the provision of public services. Public funding is not everything in the charity sector but it is much more important than Mr Cameron and others seem to understand. So is time. The Government cannot expect charities to leap into areas where the state is rapidly withdrawing. As Phillip Blond, one of the original cheerleaders for the Big Society, has warned, libraries are closing now and there is simply insufficient time for charities or neighbourhood groups to get organised and take over the running of these valuable social assets.

The Big Society is, in principle, a respectable idea. It makes sense to empower charities and encourage people to volunteer to help in their community. This will strengthen social bonds and help to benefit the most vulnerable. But what the Big Society really needs is not a gimmick-laden relaunch, but a financial rethink.