After all, the Government has been through many a bruising episode on this issue since the 1992 conference, when no fewer than seven cabinet ministers stood up in a concerted tirade against this soft target. Now, perhaps, they are older, wiser and sobered by some uncomfortable experiences. It isn't as easy as they thought.
Back to basics blew up in their face, to the merriment of all beholders. Single parents turned out not to be aliens from the lower orders but within everyone's families, including MPs'. Few families now are not touched at some point by divorce and separation, with a single parent lurking somewhere among relatives. That curious gap between policy and the real world around them has narrowed. The one piece of practical policy designed to make life harder for single mothers has been all but dropped, removing their so-called priority on housing lists.
Then there has been the fiasco of the Child Suport Agency, still collecting less money than the old system it replaced. Again, it all seemed so easy on paper, chasing the absent fathers to make them pay, instead of the taxpayer who currently forks out some pounds 9bn for single parents and their children. But mass revolt followed as fathers refused to pay. The inefficiency of an agency impossibly overstretched is still letting them get away with it. The Government's retreat in panic, allowing hundreds of thousands of non-paying fathers to escape, disheartened some of the CSA's strongest advocates. The principle was undeniably right. But ministers never anticipated the passions aroused as the agency became bogged in the mire of bitter divorces.
Moral engineering as well as recovery of money was part of the rationale behind the CSA. Threatening men with heavy maintenance payments was meant to make them hesitate to leave their families in the first place. There is no sign yet that it has had any such effect.
Even so, thinkers of right and left have not altogether abandoned their curious belief that there are levers a government can pull that will radically change people's social and sexual behaviour. Surely there could be tax incentives for people to marry in the first place? The married man's tax allowance should be increased not abolished, some have been saying loudly. But this goes against current fiscal orthodoxy, and the Chancellor has given no sign that he intends to do anything of the sort.
But the main anxiety is about the million single parents on social security. Surely here there must be something a government can do to make people behave differently? The far right, embodied by the Social Affairs Unit, believes that the benefit system is the cause of all evil. It says there would be no single parents if there was no welfare state to sustain them. Women would not dare to conceive outside wedlock, men would feel a moral obligation to marry and support any woman they made pregnant, otherwise they would starve. When John Redwood advocates adoption, this is a kind of unspoken code for the idea that removing benefits would oblige women to hand over any babies that they could not pay for to couples who could. But he dares say no more than that they should be "encouraged".
A parade of single parents from hell has hit the press in recent weeks; that handful of women with multiple children by different fathers who see no reason why the taxpayer should not pay. (In fact, on average, single mothers have only 1.7 children and only stay single mothers for an average of four years.) These stories have accompanied a clamour for something to be done, and a beady eye falls upon those benefits targeted specifically on single parents.
Critics are quite right when they point out that the tax and benefit system seems perversely to promote separation and to encourage fraud. It pays an unemployed couple to part or pretend to part and draw benefit separately. As a result there may be many fewer single parents than figures show. The CSA has uncovered massive fraud, with supposedly "absent" fathers still living at home, while drawing benefit elsewhere.
A lone mother and child on pounds 72.80 benefit gets an extra pounds 5.20 lone parent premium. It is an odd benefit as it assumes there is an extra cost for being alone when, in reality, women on benefit find having an unemployed man around is more expensive. This premium could be under threat if the Government is looking for something nasty to do. It may be an oddly construed benefit, and perhaps should be reassigned as extra for all children on income support, regardless of how many parents they have. But to cut it back would be savage.
Lone-parent benefit has also come under attack in recent weeks, for the same reason that it sounds suspiciously like a reward for bad behaviour. This is paid to all lone mothers not on social security. Its oddity, like child benefit, is that it doesn't go to the poor on income support, while it does go to the richest single mothers, whatever they earn. Its great asset, like child benefit, is that it acts as a ladder out of benefit into work. To cut it (except perhaps for the rich) would be self-defeating.
The Conservative social policy thinker David Willetts has advocated abolishing any special status for single parents. He would give all mothers income support and child benefit until their children reached the age of five, after which any unsupported mothers would be registered unemployed, and treated the same as anyone else, chivvied into work. He does not think this will happen, however, because of the cost of child care, and the the fact that unemployment figures would rise by a million overnight.
On left as well as right, they search for ways to whip people back into marriage. Frank Field, Labour's social security guru, wants to reform the whole system to help single mothers and others to escape the traps and obstacles that stop them working. But he, too, has some of the same moral engineering instincts as the right. He wants to convert the lone- parent premium into an extra benefit for couples. Would they have to be married? No, he says. Would they have to be the natural father? No. Any man dragged in through the front door would qualify then? Yes. Is any man really so much better than none? It is the doubtful thesis that strongly underlies most thinking on this subject.
However, Peter Lilley has been curiously quiet about single mothers. He may trumpet about the high levels of fraud to be weeded out, but it is likely to be a cover concealing his inability to satisfy Tory bloodlust. He may know that only child care and better back-to-work incentives are real engines for social change. Those who have been calling for cuts may be disappointed. How much can you cut from pounds 78 a week for a mother and child before people starve?