Joan Smith: Man the lifeboats! Women and children last!

That didn't take long, did it? The coalition government has been in power for less than six months but already class war has broken out in earnest. David Cameron's government as tounded its own supporters last week by announcing changes to child benefit that will make a dent in middle-class incomes, and loyal, right-thinking, Daily Mail readers didn't like it one little bit. The very people who hate state benefits and think government interferes too much in private life suddenly dis covered that hand-outs aren't just a good thing – they're an absolute bloody entitlement if you happen to earn more than £44,000 a year.

At one level, there is something deliciously funny about all this. Howls of outrage threatened to distract attention from Cameron's first conference speech as Prime Minister, and his ministers seemed to be in disarray, caught out by the detail of their own proposals. So wedded are the Conservatives to the notion of a nation made up of single-income, two-parent fami lies, that they had fallen into an ob vious trap, failing to notice that this beloved Tory icon would be treat ed more harshly under their pro posals than a couple of standard-rate taxpayers bringing in £80,000. It was a reminder that Cameron's Conservatives still aren't modern, remaining as bewildered as ever by a diverse society made up of sin gle parents, dual-income families, cohabiting and married couples.

That's why one botched an nouncement was followed by an other, a promise of tax breaks for married couples that confirmed that the Tories are out of touch and promised to throw up anoth er anomaly: weirdly, Cameron's "family-friendly" government ap pears to have committed itself to rewarding through the tax system domestic abusers who remarry, while penalising the spouses who fled from them. But even the promise of tax breaks for married couples wasn't enough to quell middle-class rage about the with drawal of child benefit from higher earners; two days ago the Mail was still describing the proposed cut as "explosive", sending a warning to the coalition that Middle England remains in revolt.

Ministers were rattled and the Cul ture Secretary, Jeremy Hunt, tried to retrieve the situation during an in terview on Newsnight by turning fire on those favourite Tory hate-figures, large families on state benefits. In a shameless appeal to class prejudice, Hunt said that the poor should have fewer children and couldn't expect their benefits to be increased if they continued to enlarge their families.

Such rhetoric is popular with some sections of the public, but it doesn't translate easily into policy; there is an undeniable link between large families and poverty – having lots of children is often a symptom and a cause of further deprivation – but it's hard to see why existing children should be punished for their parents' bad choices.

It's one thing to warn future claimants that their benefits will be capped, no matter how many chil dren they have, but quite another to apply the policy retrospectively and push kids into even greater poverty. It's also perfectly reasonable to argue for smaller families, but I can't see why the principle of moderation should apply to a couple living on a council estate in Leeds but not to an affluent family living in a four-storey house in Notting Hill.

At the same time, last week's knockabout headlines point to a con test for resources which is going to become exceedingly bitter as the coalition's spending cuts bite. Under a government ideologically opposed to the big state, it's already clear where the battle lines are going to be drawn: private sector versus pub lic sector; middle-class families ver sus the less well-off; and a north-south divide that's more entrenched than ever.

Families who live in nice houses in the South already feel squeezed; they're fed up with low interest rates on their savings, worried about their adult children's mounting debts and anxious about their own pensions. They have little idea of what life is like in northern towns, where work ing-class families have next to noth ing in reserve if public sector jobs are slashed and benefits cut.

The wealth gap in this country is shocking, and it's set to widen as Tory voters make clear that they're keen on slashing public expendi ture, but only if the pain is felt by other people.

This is the lesson the coalition is likely to take from last week's events, and ministers must also be aware that the angry middle classes will have the support of much of the media. That gives Labour's new leader, Ed Miliband, the tricky task of persuading undecided voters that he understands their anxieties while also continuing to argue that the most vulnerable members of society should be protected.

The first big test for his new team will come later this month when the Government unveils its comprehen sive spending review, but that will also be the moment when the class and gender divide between the par ties will be revealed at its starkest. Despite Cameron's rhetoric about the importance of the family, his eco nomic policies are already giving the impression that in reality it's women and children last.

June's emergency budget had a disproportionate impact on women, as an analysis published by Labour's Yvette Cooper showed. More than 70 per cent of the revenue raised from direct tax and benefit changes will come from female taxpayers; they will contribute nearly £6bn of the almost £8bn net revenue to be raised by the financial year 2014-15, compared with just over £2bn from men. Coop er described the budget as "the fiercest attack on family support in the history of the welfare state", and Cameron's faltering performance in the past few days suggests that he doesn't know what to do about this charge. He appears torn between wanting to be seen to be fair, which means spreading some of the pain, and wanting to please his middle-class supporters as they're egged on by the Mail.

It's a cruel dilemma for the politi cian credited with ditching the To ries' nasty image. The Prime Minis ter is getting a powerful message from his core vote – and what they're telling him is that they want class war.

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