All of them are at least asking a good question. If nearly half of all marriages end in divorce and if, as all the evidence suggests, the divorced are poorer and less happy, and if their children are more likely to be depressed, to truant or to become criminals, then it is surely right to ask if anything can be done.
Mr Mandelson and Roger Liddle's "government dowry" idea is certainly the most eye-catching proposal yet. Newly married couples would get the offer of an interest-free loan of pounds 5,000, financed through higher inheritance taxes. Couples would be able to use the money to help them to set up a home.
Doubtless hordes of experts and spin doctors in Tory Central Office will soon start picking it apart. It is unclear exactly how it would be means- tested, how it would be policed and whether in practice it would not just turn into yet another tax subsidy for the banks and building societies.
But it will be hard for the right to be too critical because this proposal is only the latest in a long stream of attempts to use financial incentives to reverse the tide of divorce. Only last year, a group of Tory ladies proposed that a lump sum should be given to married couples who had stayed together for 10 years (this at least had the virtue of recognising that the real problem is not a shortage of marriages but rather a shortage of successful ones). There is also a strong likelihood that Downing Street will conjure up its own marriage bonus in time for the general election.
Many of these make good symbolic politics and doubtless the dowry idea would be popular, especially among working-class couples who would like to be able to afford a white wedding - such a wedding in the South- east is now estimated to cost more than pounds 8,000 - and a down payment on a mortgage.
But the conventional wisdom that relationships can be seriously influenced by economic measures rests on a fundamental misreading of the situation. In the past, marriage was above all an economic institution. You had to get married to survive, just as you had to have children to ensure that you were looked after in old age, and you judged your prospective partner in terms of their ability to earn, to bear children, or to cook.
Today our whole attitude has changed. In the Fifties, surveys found that the most important things in marriage were the efficient fulfilment of the roles of breadwinner and homemaker, but by the Eighties they found that the most important considerations were faithfulness, mutual respect, understanding and tolerance. We now look to relationships and marriage for love. We expect our partner to be our best friend and most intimate companion, as well as a co-signatory on the joint mortgage.
This is not to say that money is wholly unimportant when it comes to settling down or choosing your partner, but marriage today is not primarily about economics, just as the failure of marriages is not primarily about having the wrong incentives. After all, the sixfold rise in the divorce rate since the early Sixties came before the decline in real terms of the value of the married couple's tax allowance, which began in 1990. And the prospect of poverty after divorce has not prevented women (who initiate most divorces) from leaving unhappy marriages.
The real problem is that we have far greater expectations of relationships, and much greater freedom to walk away from them, without having the skills we need to manage relationships well. Our attitudes to marriage are far more transactional and we are far more willing to react quickly if we feel that our partner has broken the contract. Yet we have not learnt how to negotiate, how to communicate well, and how to reconcile the inevitable clashes of interest and emotion.
If you had a couple of billion pounds to spend on improving family life, my guess is that you could spend it far better on helping people to stay in relationships than by encouraging people into commitments they are not ready for. As well as better pre-marriage counselling (which is already common in America and Australia), we also need to do far more to help couples in the early years of marriage, particularly when children are being born, rather than only when relationships are breaking up. Yet at the moment the Government spends 1,000 times as much picking up the pieces from family breakdown as it does on marriage support services. A sensible policy would also make it easier to balance work and home. The number of divorces granted to couples with children under five has increased by two-thirds since the mid-Seventies. Yet Britain is the only country in the EU to opt out of providing three months' unpaid parental leave (an issue on which new Labour remains silent).
There is no prospect of returning to ordered relationships of the past. A fairly chaotic world of love is the one we now live in, and if we are really serious about making families happier it is going to take more than Pat Buchanan endlessly telling us that "the momma bird makes the nest", more than tax incentives and more than new Labour's promise of a government dowry.