Gordon Brown is looking for a big idea. In search of one, he put Martin Taylor of Barclays Bank in charge of a tax and benefit task force. Its ambitious remit is to streamline the system, to increase work incentives, reduce poverty and strengthen community and family life. The dream is to find a way of integrating tax and benefits, creating a smooth transition from one to the other, ironing out work disincentives and social stigma as it goes.
It is, however, a fiendish conundrum, a Holy Grail (or maybe fool's gold) that has eluded many sharp Tory brains who had almost precisely the same intentions. There they go again, rediscovering the same old see-saw, every bright idea balanced by an equally heavy downside.
In his budget speech the Chancellor seized hold of an American scheme called Earned Income Tax Credits. He ordered the task force to consider it and he has been plugging it ever since. Now many fear that he may push it through because it sounds good, despite its many drawbacks.
The idea is to build work incentives into the income tax system. Currently Family Credit is the work-incentive benefit: it tops up low pay, ensuring it's always worthwhile to work, even in a low-paid job. Brown's idea is to transfer that into the tax system, calling it a "tax credit" to make it more socially acceptable to claim.
But, amid growing alarm at Brown's enthusiasm, the notion is getting an emphatic thumbs-down from all the experts. It would bring a huge administrative upheaval for very little good effect: there is little evidence of social stigma against claiming Family Credit, since its take-up is now more than 80 per cent.
Turning the benefit into a tax credit would have deep drawbacks. Instead of the benefit being paid out in the usual way, employers would have to operate the scheme, hugely adding to the complexity of PAYE. Employees wanting to claim would have to give to their bosses details of their lives, partners, children and savings - hardly a popular move. Employers would have to assess the information, pass it on, and then hand over the extra cash, instead of just collecting the tax in the usual way - tough on their time and their cash flow.
It would risk making employers keenly aware of how to take unfair advantage of Family Credit, by paying low wages and hiring only staff who qualified for the benefit. At the moment, employers are largely ignorant of it, because it does not pass through their hands. Worst of all, Family Credit would be transferred into the husband's pay packet, and no longer be paid to the wife. Yet the research suggests that more money is spent on children when paid to the mother, not the father.
Tax credit is an idea whose time has come - and gone - in the space of a few short months. But the Taylor committee will still need a big idea, because Gordon Brown needs a big idea. Here, then, is a big one, but it really does mean thinking the unthinkable. It means thinking again about women and men in the tax and benefits system.
First, I will admit that I and a large number of women who campaigned for separate taxation for husbands and wives were wrong. Introduced in 1990, this feminist move gave married women separate taxation and a separate tax allowance for the first time. But it boosted the earnings of better- off couples and widened the gap between two-earner families and the rest. Now it is time to think again.
A growing number of experts, including some Brown advisers, are saying that taxing couples independently was a seriously retrograde step. It gave well-off, dual-earner couples pounds 1,000 extra, costing the state some pounds 2bn a year. And yet, though many wives work, they continue to be regarded as "dependants" in the old-fashioned way - which entitles husbands to the Married Couples Allowance of another pounds 250 a year; that costs the nation another pounds 2.5bn.
Women campaigned for separate taxation not out of greed, but as a protest at the indignity of the previous system. The husband filled out the family tax form in his own name, demanding to know every penny his wife earned or saved, without the wife necessarily having access to the same information about her husband's money. But if couples were jointly taxed again they should sign the form jointly, with transparency on both sides. After all, poor couples on social security have never had independent rights. They are assessed jointly - though this new deal should include allowing women to draw their own benefits and their children's separately, instead of their husband collecting the lot.
Joint taxation (for those who cohabit, as well as for the married) would mean that for the first time it would become worth taxing Child Benefit. If you tried it now, it would hit too small a number of high-earning mothers to be worth it.
So if you took all the money collected from these three measures - joint taxation, abolishing the Married Couples Allowance and taxing Child Benefit - you could double Child Benefit. I have always been against increasing Child Benefit, as too much is wasted on women like me, who don't need it. But that objection fails, once you can tax it effectively. Then Child Benefit becomes the best way to get parents off social security and into work, as it creates no poverty trap. It also gives women everywhere more money in their hands to feed their children in a crisis.
This would be a redistributive act, taking from well-off couples and giving to poorer families with children, mainly taking from men and giving to women. But it would be a great deal more popular than using the income tax system. Those men who lost out would no doubt feel hard done by. But their complaints would be drowned out by all the delighted mothers who would get twice as much Child Benefit in their hands each week.
Would there be a great feminist outcry at returning to joint taxation? I think not, if that were the quid pro quo. Child Benefit is immensely popular, even with men. Now there is a big idea that hits every single one of the Taylor task force's targets. Forget fiddling about with tax credits, and go for doubling Child Benefit.