This is what Lilley has done: in the Budget the Chancellor announced that the Lone Parent Premium, (pounds 5.20 extra for single parents on income support) and One Parent Benefit (pounds 6.30 for working single parents) will be axed. It was a neat ploy, signalling moral disapproval of single parents while saving pounds 100m a year.
Harman protested that the cuts would hit the weakest but otherwise no great cry went up. The silence was eerie. Once, hundreds of thousands would have been out on the streets in protest, but times have changed: people are resigned to government callousness, or simply don't care. Single parents account for most of the huge growth in poverty. They are the most vulnerable group, so cutting their benefits is dangerous cruelty. But to cut the premium that helps those in work is plain madness, as many will sink back into unemployment. This is one of the most monstrous things this government has done - though you wouldn't think so from the lack of public indignation.
Be that as it may, this is the Tory Social Security Secretary's trap: to make these cuts he must consult his Advisory Committee, then put a Bill through Parliament. That cannot be done before June - by which time Labour could be in power. So will Harman, as her very first act, implement these cuts, or will she find pounds 100m to plug the gap that Brown is committed to keeping at its present level?
Here is Lilley's triumphant letter:
"This afternoon Gordon Brown pledged to stay within the public spending limits. Our spending plans depend on retaining and implementing my social security reforms. Yet you have opposed or criticised all these reforms. Can you confirm ... that you will introduce in government our proposed legislation ... for single parents ...
"Will new Labour carry through these Conservative policies which you have criticised? If not, what other specific programmes will you cut to keep overall spending the same? You cannot duck these questions: people will know that evasive waffle in Opposition means expensive whammies in Government.
"Yours sincerely, Peter Lilley."
The increasing use of the unconditional future tense - "you will introduce in government" - may be gratifying evidence that Tory ministers have already given up the ghost, but such questions still have to be answered in every department. Harman declined to step neatly into his trap. She side-stepped, replying:
"By using money from a windfall levy on the excess and unfair profits of the privatised utilities we will get 250,000 under-25-year-olds off benefit and into work and create opportunities for people who have been unemployed for over two years by offering a National Insurance holiday to employers who take them on ... A Labour government will inherit a social security system which you and your government have made expensive for taxpayers and degrading for claimants. We will have to start work immediately on making the system fairer.
"Yours sincerely, Harriet."
So, will she or won't she introduce Tory legislation to cut single parents' benefits? "No, of course not," she says when asked. So how will she pay for the shortfall? By getting many of the 1 million single parents on benefits back to work and saving their income support. 500,000 of them have a youngest child aged five or over and they could work, at least part time, if someone gave them a push. The part-time jobs are there and Labour has promised the necessary after-school clubs from the lottery fund. Currently, single mothers just receive a letter once every three years and are not registered unemployed, and no one urges them into work.
Maybe, then, she can escape this particular trap, if Brown is satisfied with her reply. But the last budget, as it is analysed more carefully by the experts, contains all kinds of deliberate dishonesties - land- mines for incoming ministers trying to keep within its impossible limits.
Just take some of the social security estimates, for instance: the Budget reckons a new Fraud Bill will save pounds 7bn, but few experts think so. pounds 1bn is supposed to be saved by a new DSS computer; others strongly doubt it. Estimates for social security land sales are extraordinarily optimistic. Never before has the DSS deducted a notional sum for an expected fall in unemployment (increases during bad employment years were never added.) "Honest" Ken Clarke knows he won't be facing the music, so he has produced a budget full of holes. If, by some miracle, he finds himself back in the hot seat come May, then he will simply put up taxes to cover the shortfall. If not, then Brown has foolishly swallowed his bait by promising to abide by an unworkable budget.
If things look grim in social security, that is nothing compared to the calamity that will hit the incoming health minister. In the last 17 years, NHS real growth has averaged 2.6 per cent a year. But the limits Brown has signed up to are: this year the NHS gets only 0.9 per cent, next year 0.8 per cent, the year after 0.7 per cent. Clark must be laughing up his sleeve, for out there in the long grass are plenty more leopards awaiting their Labour shadows.