So the Conservatives propose to give £2.88 a week to married couples on low and middle incomes, but only if one of them doesn't work. It doesn't matter whether or not Mr and Mrs have children – they'll get the tax break anyway. The critical factors for the Tories are that: 1) said couple are lawfully wed and 2) one of them opts to stay at home. And, not withstanding the ever-mushrooming number of househusbands, the spouse staying at home with the Fairy Liquid will still, in the overwhelming majority of cases, be the bride not the groom.

You don't even get to join the queue for the Tory tax break if both you and your spouse go out to work, or if you are merely long-term cohabitees – however many children you may have. And if you are a single parent you are, inevitably, persona non grata. Because despite the Conservatives' scramble to portray themselves as family-friendly, this is not actually a tax break designed to help families with children, but one aimed instead simply at shoring up the institution of marriage. The self-styled modern, progressive Conservative party is firmly wedded to practising social engineering through the tax system.

Fortunately, however, even if we have the misfortune to elect a Conservative government, this policy will have very little impact on the lives of middle income families. (Don't be lulled into thinking that other Tory policies fall into the same category though – you'd certainly notice their cuts to Sure Start children's centres, to child tax credits, to child trust funds and to the schools budget.) But, in the real world, no one will decide to get or stay married for the sake of £150 a year. A working woman won't suddenly ask for her P45 when she ties the knot in return for a state dowry of £2.88 a week: it's not as if you can adopt the lifestyle of a lady who lunches when your entire weekly tax break won't even stretch to a Boots meal deal. I am not suggesting that £150 is a sum to be sniffed at, because it isn't – indeed, if it was given as a lump sum (which it isn't), it would certainly cover a week's shopping at Tesco for a typical family of four. But it's hardly enough to shape behaviour or make any kind of difference.

The Conservatives know this, of course. Which is why they say that their marriage tax break proposal aims merely to 'send a signal'. That is certainly true. But, make no mistake, the signal is not that Tories in 21st century Britain value hard-working families of varying shapes and sizes. Rather, it is that a marriage where the wife is wed firmly to the kitchen sink is the most highly prized. There is no shortage of adjectives to describe this policy, but modern and progressive are not among them.