IT'S barely a week since the furore over tax evasion by the rich and famous, and the PM has decided, once again, to target those at the opposite end of the spectrum: the poor, weak and vulnerable.

As part of his attack on the so-called "culture of entitlement", he wants to restrict income support and possibly child benefit to single mothers with three or more children.

Given that Mr Cameron's welfare cuts have been cut-throat, maybe this latest proposal – one of 17 ideas for reforming the benefits system – shouldn't surprise me. But then I can remember Mr Cameron pledging to back the very people he's now trying to wield his benefit-cutting axe against.

Just last year, he said: "Leaving single mothers, who do a heroic job against all odds, to fend for themselves simply isn't acceptable." And in 2010, he asserted: "To that single mother struggling and working her heart out for her children, we can now say: 'We're on your side'."

Doesn't seem like it. While I appreciate that during a time of austerity tough choices must be made, single mothers are the wrong target.

Statistically speaking, Britain's two million single parents and their children are already the poorest in society and according to the charity Gingerbread, 41% live below the poverty line.

But Mr Cameron wants those of us who do things the "right way" – ie get married and work hard supporting our kids – to be annoyed by the teen mum who gets given a council house and has a baby, then has another and another until she's taking in an income of up to £25,000 or so in benefits.

I'm about to have a child, and my husband and I worked and saved until it was the right time to start a family. So it would be easy to fall for this kind of rhetoric. I also support Mr Cameron's belief in the importance of marriage, and sympathise with his regret at the breakdown in family life in society.

But singling out single mothers for chastisement smacks of class prejudice, outdated morals and divisiveness when, in fact, fewer than 2% of single parents are teenagers and around half of single parents had their children within marriage (49% are separated, divorced or widowed).

Some 150,000 people with three or more children have been claiming income support for more than a year. Of those, 57,000 have four or more children, and Cameron claims restricting child benefit to three children would save £300m a year.

I say these figures are a drop in the benefits ocean. Given that Mr Cameron has previously stressed the disadvantages children from single-parent families face, it seems contradictory to introduce a measure which, in the end, would surely only punish them more.

It's easy to make snap assumptions about single mothers, when in fact, 57.2% of lone parents are in employment – a figure that rises as the children get older. Are there a small number of women who choose to get pregnant and live off the state? Undoubtedly.

But if Mr Cameron thinks his measures will do anything to change this minority attitude, he is being naïve. Restricting the number of children you can have before losing benefit is a dangerous idea.

And is cutting benefits really going to push people into the workforce at a time when there aren't enough jobs to go round? Even if it did, the high cost of childcare already means 46% of single parents rely on informal childcare.

The Prime Minister wants to create a situation where single mums are not better off out of work than in it. But that's unlikely, given that the poverty rate for single-parent families where the parent works part-time is 23%, and 18% where the parent works full-time.

Single mothers on benefit are hardly getting "something for nothing". It's a wonderful thing that women in this country can feel safe in the knowledge that they are not dependent on a man to look after them; that, with the help of the state, they can take care of those children themselves.

David Cameron must take a step back and consider the moral framework that makes this country, and its welfare state, something we should be proud of.