I remember an acquaintance, let us call her Victoria, bemoaning the fact that she couldn't possibly afford to work part-time after the birth of her child; couldn't afford to lose a fifth of her salary - about £15,000 - without her life falling apart.

That's 20 per cent of the salary, by the way, the £15,000, not the actual salary.

I think I raised half an eyebrow; what I wanted to do was slap her. This woman had a husband earning well over £100,000 a year, two homes, two cars and all the accoutrements that go with that sort of lifestyle, such as expensive friends, skiing trips and other holidays.

What is one person's necessity is another's luxury. And that is precisely the problem with the proposal this week, from a think-tank close to David Cameron, to give all mothers £50-£60 a week per child, from birth to 3 years old. That's on top of child benefit, so getting on for £4,000 a year for each child. Necessity, or luxury? And there's the nub. For Victoria, that £4,000 would be a luxury. It might pay for the skiing trip, I suppose. But look who is going to fund it. The proposal from Policy Exchange is to use the money from the childcare element of the working tax credit and from Sure Start maternity grants, funds that currently go to the poorest working mothers, to pay for the new parental care allowance. And even that would only cover about a third of it.

Now I'm as open to being bunged £4,000 as the next mother, but it so obviously isn't fair. What is amazing, then, is that Maria Miller, the Conservative Party's Shadow Family Minister, turned up to the launch of the report on Monday and made encouraging noises about it. She didn't go so far as to say that the Tory party would adopt the idea, but she did welcome it and say that the Conservatives would consider the recommendations.

There couldn't be a clearer example of robbing the poor, who can get up to £240 a week for childcare under the working tax credit, to give to the rich. That £4,000 isn't enough to support a mother who doesn't have any other income. She would have to go to work anyway - if she could afford to do that without the childcare help available under tax credits. If she couldn't, I suppose she could have a lot of babies very fast, raking in £4,000 a year for each of them. What a good idea.

The proposal is immoral and regressive, hurting the poorest children the most - something that Ms Miller recognises. Yet she has still allowed herself and the Tory party to be associated with the proposal, which chimes with various things that Mr Cameron has been saying about giving mothers more choice in the early years. It's a classic middle-income vote-winner, handing out cash to people who do not really, really need it.

And many mothers will embrace the idea. There is this sense of entitlement that comes over so many women, encouraged to think that there is something selfless about having children, once they have produced a sprog. I'm producing the next generation of taxpayer, they intone piously when pressed - as if that is really the reason why they gave birth. The indignation in Victoria's voice that she be expected to work full-time or give up one of her annual holidays, or perhaps the account at the organic butcher, was nauseating. I have heard it again and again: well-off women moaning about the cost of nannies, the juggling, the “lazy” husband (more often than not working his dull socks off to support her time off) - what part of having children did they not understand? “I don't know how she does it”? Usually with a full-time nanny.

You have children, you give something up. That's the deal. It might be income, it might be friends, it might be expensive holidays. And if you are really, really lucky you might be able to afford not to work for a few years. What you do not have is the right to expect to be paid by the taxpayer to stay at home. Especially when you do not really need the money.

For it's not a zero-sum game, a woman leaving the paid workforce. She - and now her children - still uses public services, doesn't she? The doctor and the subsidised trains, the schools, the roads, the health visitor, the library. And she has stopped paying for them. So you see, every non-working mother already gets a large subsidy from the State; less, perhaps, if she has a working husband, but still a subsidy. Have you seen how mothers of young children guzzle public services?

There is another argument why the State should not be encouraging women not to work: it is very bad for them. Mothers who haven't worked, not even part-time, for three years, or longer if they have had more than one child, will find it very difficult to go back into the workplace. They lose confidence and the routine of work. They have fallen behind their peers. They have forgotten how to do it. They may never go back. That isn't good for the mother and ultimately it isn't a good example for the children either.

I understand the reluctance of mothers with young children to farm them out to nurseries. Much of the problem with that, though, stems from the standard of care in the nurseries themselves, and the amount of time the babies have to spend in them. Encourage more flexible and part-time working, as the Government is doing, and pay childcare workers more to get a higher standard of care and slower turnover of staff. That would be a better investment of the £5.4 billion that the parental care allowance would cost.

But it wouldn't help Victoria, who now has a live-in nanny. She's still moaning.

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