We seem to have reached a point in this election where everyone agrees on the main issues, such as the necessity to cut almost everything, so the parties are desperate to come up with policies on the more peripheral issues. They must sit in their offices going: "We could propose immigrants should have to learn to juggle?" Or: "I know – strike ballots won't be valid unless voting forms are sent to all union members' pets."

That must be how the Tories came up with their plan to "strengthen marriage" by rewarding some couples with £150 tax relief for staying married. Because that's how marriages break up.

Couples scream with anguish at each other while the kids plead for them to stop, then sob themselves uncontrollably to sleep in bewilderment at how their love has turned to such animosity, until they conclude that the situation is irretrievable and in desperation one of them goes to live on a mate's settee while they draw up arrangements for access to the children, and all the while they're thinking, "The one thing that would have kept us together, is £2.87 per week tax relief, subject to alterations in the basic allowance."

So they need to go further. No marriage can stay strong without a healthy sex life, so a further allowance, worth around £65, should be available to couples who make love twice or more each week on average throughout a tax year (April to April), as long as they provide proof of completion of the act to an officer from the Department of Works and Pensions. That should stop adultery. No one is going to have an affair if it's going to lower their married man's annual tax threshold.

In some ways this is a classical Conservative attitude, that marriage is noble and worthy of reward in itself, whereas a marriage breaking down should be punished. Maybe they should strengthen marriage further, by bringing in a law that any couple finding their marriage in trouble should have to go to Relate, where they get zapped by a Taser gun. Then they'll stop bickering over housework.

The idea is that couples "split up easily these days", especially if they are not married. Whereas when married couples hit a difficulty one side will say, "I'm not bothered about the house, and the kids I can take or leave, but if we divorce I'll have to fill in a form and I'm not going to all that trouble."

No one participates in the breakdown of a household lightly. The next Tory proposal might as well be that as part of a drive to combat dementia, they're going to offer tax breaks to the elderly as long as they can keep remembering things, with £15 added to their winter fuel bonus if they can go right through Christmas without wandering into a room and staring blankly. Then they might learn not to be so forgetful.

It's as if genuine romance, untouched by the pressure of tradition or financial incentives, is beyond their understanding. Maybe David Cameron has a vision that young men will turn nervously to their partners and say, "Sweetie, there's something I want to ask. We've been together two years now, and I've been thinking, well in fact I've even asked your father and, well, if we get married before the end of February we can apply to have a portion of our married person's added tax allowance carried forward into the following tax year, which could even affect our Isa."

But the outlook that the motivation for everything is money is shared by New Labour. So they might try to trump the Tories by promising to modernise marriage, insisting that before anyone proposes they have to put themselves out to tender and consider at least three rival bids, of which at least one must be made by Balfour Beatty.

The scheme will be called the Private Partner Partnership, locking both sides into a 25-year deal, at the end of which you will be given the option of buying yourself back.

Labour seem as incapable as ever of combating the Tory gimmicks, as they have done so much to create this culture in the first place. On top of that, if it was Labour that had proposed this scheme the Daily Mail would have gone berserk, saying this would lead to a flood of immigrant Mormons, Arab Sheikhs and Chinese emperors, all coming over in their millions with their 50 wives each to enjoy our generous marriage tax allowance.

So there is little they can do except express their own allegiance to marriage, the tradition that has provided the foundation of stability in British life, from Henry VIII to Prince Albert, Charles and Diana, and to Fred and Rose West.