Leading article: Still playing the class card

There is more than one middle class in this country. Which is why the Prime Minister's mission yesterday to present Labour as the champion of the middle classes was always going to be a tricky assignment. He claimed in his speech that he was "born and brought up in Britain's middle class", but the Scottish bourgeoisie is different from its English equivalents: whether the public-sector middle class or the capitalist managers; whether London or provincial; or whether it is the middle class in the American sense of anyone with a permanent job above the level of the minimum wage.

Mr Brown pitched his speech at those whose "dreams" were "owning a bigger house, taking a holiday abroad, buying a new car or starting a small business". On a day that £10m was raised for the Disasters and Emergency Committee appeal for Haiti, this struck a discordant note. Even in the absence of an urgent humanitarian crisis, we imagine that the readers of this newspaper might harbour dreams that extend beyond material comforts and status symbols.

It just shows how careful politicians should be with the hidden meanings of class. Assumptions of social station lurk beneath the surface of all manner of issues of party-political contention. Take the yearning for a "return" to an imagined golden age of responsibility, civility and stable families. Just how ticklish family policy can be is illustrated by David Willetts, the opposition Families spokesman. As we report today, he got into a terrible tangle in trying to explain to the BBC how the Conservatives want to support marriage through the tax system but that they are not trying to send a "message" about what kind of family is preferable – thus contradicting not only himself but his leader, who said that the tax break for marriage (and civil partnerships) was "about the message more than the money".

Or take the resentment of car drivers that minor infractions are used as a revenue stream – a resentment that is often justified, as we report today. Speed cameras are widely regarded as a conspiracy against the middle class, a way of raising money easily from respectable people rather than pursuing really dangerous or uninsured drivers who are hard to bring to justice and yield little money.

So when Gordon Brown says that he was "always taught that hard work, effort and responsibility were what you needed to make your way in the world", we know what he means, of course. He has been criticised for tilting towards a core vote strategy, of pitting the interests of the poor against those of David Cameron's privileged chums. Yesterday's speech, therefore, was all about putting Labour on the side of people on middle incomes that would, allegedly, be "squeezed" by the Conservatives.

But even if the election were determined simply on what Americans call pocketbook issues, this is a hard sell. The idea that most middle-income voters believe that their household finances are going to be hit harder by a Tory government than a Labour one is sufficiently counterintuitive to require more than one speech from the Prime Minister and a press release from Labour HQ. The press release said that the Tories would cut child tax credits, trust funds and Sure Start for better-off families. But Mr Brown's continued reluctance to talk about public spending cuts invites most middle-class voters to draw the conclusion that they will end up footing the bill. He ought to remember that honesty and thrift are middle-class virtues too.

Mr Brown's clunking attempt to lay claim to the politics of aspiration failed to address this. Nor is "social mobility" the kind of slogan that people would stitch to their banners. It is not exactly the language of the Chelsea tractor school run, so it lacks any emotional appeal to make up for its intellectual vacuity. Indeed, "social mobility for the majority", which is what Mr Brown said, invites questions rather than answers them. How many of the majority are going to be downwardly mobile? Does it simply mean greater prosperity for the majority? What about the minority?

This is a pity, because Labour has a good record of widening the opportunities previously open only to tiny minority in schools and universities, and extending the benefits of a middle-class life throughout the country. It also has an important case to make for the future: that protecting employment and public services is in the interest of people of all classes. Mr Brown should stick to making that argument rather than trying to appeal so clumsily to sections of the electorate, especially ones so ambiguously defined as "the middle class".