Sean O'Grady: Taxing the rich may impress the voters, but these policies don't stand up under scrutiny

In his foreword to the Liberal Democrat "pre-manifesto", Charles Kennedy says that he is sometimes asked: "You Liberal Democrats are doing very well, but what do you really stand for?".

In his foreword to the Liberal Democrat "pre-manifesto", Charles Kennedy says that he is sometimes asked: "You Liberal Democrats are doing very well, but what do you really stand for?".

I'm not sure about the literal truth of those words. One doubts that, as he was successfully tramping the mean streets of Leicester South and Brent East, many quizzical citizens greeted him with that stilted inquiry.

Generally, Liberal Democrat supporters have displayed next to no interest in the party's policies. (The unkind might add that much the same applies to Mr Kennedy.) The party's appeal has famously been as a protest against whichever of the two parties that happened to be in power. Sometimes the official opposition has been so feeble - Michael Foot's Labour Party, William Hague's Tories - that people have turned to the Liberals to protest about them as well.

Mr Kennedy has been doing good business simply by being neither the allegedly duplicitous Tony Blair nor the supposedly extreme Michael Howard. Yet the Liberal Democrats have always been vexed by people's reluctance to vote for them rather than against someone else. Their self-prescribed treatment for this anxiety is to get cracking on a new policy document. This is the latest. Much of it is familiar. Gone may be the ritual promise to raise the standard rate of income tax by one penny, if necessary, to pay for improvements in education.

But the promise to tax the rich remains. A new 50 per cent rate of income tax on the last slice of annual earnings over £100,000 is designed to raise enough to pay for three specific improvements in public services: scrapping tuition and top-up fees for students; introducing free personal care for the elderly and disabled; and getting rid of the council tax.

As a positive pitch it is clever, combining three or four impeccably populist causes. No one need ever again lose their home to pay for care. Students can forget debt and get on with learning and enjoying themselves. The rich, and only the rich, will pay. It should do well on the doorstep, as it has already for the party in Scotland, where it has had a share in implementing some of those policies. It might even create a strange dual "core vote" of those just entering and those just exiting the political market place. The middle classes of all ages should love it. It should work. The real question is whether it deserves to.

For there is a certain lack of courage in this pre-manifesto. OK, in a good year for the economy £4.3bn might well be raised by taxing the rich, but what happens if growth stalls? On that possibility the pre-manifesto is silent. Most pitifully of all, it pays scant attention to the cause of the euro and has little to say on asylum and immigration. Whatever you think about their past approach on these issues at least they lived up to Keynes's invocation to "appear unorthodox, troublesome, dangerous, disobedient". No longer, it would seem.

The writer is a former press officer to Paddy Ashdown