This week a group of Tory MPs has flocked to a dear old barricade against that implacable enemy - the permissive society. In the name of the family, they killed Lord Mackay's domestic violence Bill and took aim at his divorce reforms. Meanwhile, with equal vigour, they fought off attempts to clean up their own act. To most Tories, Lord Nolan's demand that they register all income derived from their positions as MPs is as unpalatable as orange juice at a parliamentary cocktail party. Next week, they are pledged to throw it out of the Commons.

It is doubtful whether the public is much impressed by our legislators' public ruminations about issues like marriage and divorce. Why should the intervention of these largely middle-aged, mostly male, not infrequently divorced politicians working long hours in an antiquated atmosphere carry great weight in the ordering of our personal lives? Most people wanting to hear something sensible about relationships would be better off with an agony aunt.

Nevertheless, it is plain that we are lodged in a serious phase of parliamentary moral breast-beating. This is partly caused by the intensifying conflict between the parties as the election approaches. Mr Blair sees commitment to solid, old-fashioned family values as a way of promising voters a reprieve from the insecurities of the age and, more pragmatically, as a means of securing his hold on the centre ground of politics. The Conservatives' desperation to resist this incursion tempts them, not for the first time, towards a rightward drift, challenging Mr Blair to wander further into the woods of social conservatism. Perhaps, just perhaps, he will get lost there and be knocked on the head by a mugger or out-of-work squeegee merchant.

There are also more underlying causes for this anti-liberal swing. Many people genuinely regret the demise of old moral certainties that have disappeared with the waning power of the churches, political leaders, teachers and other traditional authorities. The choices many of us make in life are all too often accompanied by trauma, emotion and guilt. Right- wing Tory MPs sense that a burst of fundamentalism stands a chance of making us all feel better. It is little wonder that a number of Conservatives have been drawn into the Roman Catholic church, which has made so few concessions to liberalism.

But most of us also know that this is essentially nostalgia for a golden age. We may regret that our brother or sister or mother or father or best friend is divorced, we may have acute concerns for the children and be anxious to provide support, but we do not any longer think we can change the way things are. The forces that have broken down the old patterns are more powerful than that and it is political self-delusion to think that they are really much to do with the workings of the welfare state.

The high divorce rate is in reality impervious to the hectoring of politicians. Nor is it likely to fall if marriage attracts, as some advocate, extra tax advantages. Divorce involves great losses in terms of income, friends, children and homes. But once a marriage has failed those involved, especially the women, still press ahead with separation whatever the cost.

This freedom of choice does not, as some Tory MPs might argue, mean that we have become an amoral society. Quite the opposite. This is a highly moral age. Multiplicity of choice can make us pragmatic, expedient and selfish. But it also forces us to generate and frame our own moral codes, instead of, as in the past, passively adopting a set of principles handed down from above. Do we really think that we or those around us are less sensitive today than we were one or two decades ago about the conduct of personal relationships, violence, honesty, discrimination, not to mention the new moral complexities that arise from advances in genetics and other medical technologies?

There are many sources for the pick'n'mix morality we all use to tackle these questions. The churches used to be like giant conglomerates supplying everything needed. But today a differentarray of voices challenges us. Pressure groups and charities make their arguments about pollution, animal welfare and poverty in the Third World. Feminism has redrawn the force- field around relations between men and women. Soap operas, Kilroy, Richard and Judy, Oprah all confront viewers with tricky issues. It may be more difficult to know what you think, but there is plenty of thinking going on. The biggest danger is that it all comes to seem so complex that the individual feels powerless to make a difference. That should be a prime point of entry for the politicians, but it won't happen if the politicians we encounter are not describing the world as we know it to be.

Greater individualism has not produced anarchy, just complexity and a great deal of personal agonising. It is compatible with a well-functioning mass society, just as the millions of different preferences expressed by consumerism are consistent with a modern, efficient economy. Despite the development of individualised morality, there remains enough of a common culture to keep society functioning. We no more need Parliament to make us stay married than we need it to run a command economy.

So what is the role of politics in the realm of morality? This week, right-wing Tory MPs seemed to to be bidding for territory vacated by the bishops. Even though the churches, including the Roman Catholics, had endorsed Lord Mackay's divorce reforms, they took it upon themselves to lay waste his proposals. This is not helpful. Politicians need to show some humility on matters of personal morality. They should remember why John Major's "back to basics" campaign foundered in the most garish tabloid newspaper headlines.

They should also think very hard before they say no to Nolan. A long series of incidents has convinced many voters that Britain's legislators are unprincipled and open to corruption. A very large amount of this is unfair but it has to be faced: these days ministers are trusted even less than journalists. Lord Nolan recommended that the sources of MPs' incomes should be made transparent. His purpose was to restore their credibility and prove that members of parliament have nothing to hide. Even those MPs who do not like the rules in detail should recognise that Nolan has offered them a stepping-stone back to the kind of firm ground politics needs if it is to be healthy, vigorous and relevant.