What gives bishops the right to tell us how to vote?

It is usually sex which gets the Catholic Church into the headlines. Contraception, abortion, cel-ibacy, misogyny or sexual abuse by priests - such is the stuff of which news is normally made by what appears to be a sex-mad church in a sex-mad world.

But today its bishops venture into a new area of controversy - one which hitherto has been the preserve of the Church of England - politics. The manifesto for a better Britain which they launch today has already been dubbed by one Catholic paper "The Bishops' Guide on How to Vote". The fact will surprise many, yet anyone who knew anything about Catholic Social teaching might have seen it coming.

Not that many people do know anything about it. Though Catholicism's own brand of communitarianism has been steadily and comprehensively developed over the last century, under nine popes, it has been little publicised. "The Church's best kept secret" is how one wag branded it.

Yet, if some will suspect the bishops of England and Wales of being political in the timing of their campaign to make this doctrine better known, they cannot be vulnerable to the charge that their social policy has been made up as they went along, at the whim off the latest fad or ideology, or by arbitrary exercise of their individual consciences.

In a sense, of course, the church has always had views on social issues. The Old Testament is full of concern for the poor, the widow and the stranger, and the New extended that to a wider group of the marginalised and oppressed. Throughout history it has been played out in different forms.

The early decades were characterised by a "love communism" as possessions were pooled by the first Christians, who thought that goods were unimportant since the world was just about to end. Later, when the faith was institutionalised under Constantine, and in the millennium of Christendom which followed, it developed a feudal sense of common purpose. For this the great medieval theologian Thomas Aquinas coined the phrase "the common good" - which 800 years on is the name the English and Welsh bishops have given to the document they publish today.

But it has been the battle between capitalism and communism which has forged the coherent philosophy which undergirds today's raft of episcopal proposals. The result is a collection of policies which defy neat party- political categorisation, though no doubt many will try to cram them into such a template in the coming days.

Controversy has bedevilled the church's social policy since the publication of the first of its 14 major social encyclicals. Rerum Novarum, by Pope Leo XIII, was published in 1891 as a response to the rise of communism. Faced with the industrial revolution, the exploitation of workers and the greed of a "tiny group of extravagantly rich men" its conclusion was -mildly - to ask the poor to be patient and the industrialists to be more careful. Yet it was condemned at the time as a socialist document (even though it specifically attacked socialism) because it proclaimed the primacy of people over things.

On that premise today's bishops base their unfashionable insistence that labour must take precedence over capital. The document which they want five million Catholic voters to consider before the general election, has hard words to say about the "dumping" of redundant employees in company downsizing operations during the takeovers, closures and mergers which the bishops condemn as a significant cause of modern social injustice.

Long after Rerum Novarum, the church remained on the side of the rich. Forty years later, Pope Pius XI acknowledged in Quadragesima Anno that capitalism spread "all the errors of individualistic economic teaching... which lets only the strongest survive ... those who give least heed to their consciences". But he had no solution in mind. He simply made a plea for social responsibility, and articulated for the first time the principle of subsidiarity - that decisions should be taken at the lowest level consonant with good government - in an attempt to minimise the concentration of power in the hands of a few. His successor, Pius XII, concluded after the failure of fascism that capitalism was the only way to safeguard freedom and combat both poverty and communism.

Everything changed with the Second Vatican Council in 1962. The revolutionary gathering of pope and bishops - which with its first public document ended the Latin mass which had been the norm for 15 centuries - transformed the church. It began the council a closed, hierarchical institution focused on its sacramental life. It ended as a body which looked optimistically out to the world to read what the council's closing document, Gaudium et Spes, in 1965 called the "signs of the times".

Vatican II reduced the church's reliance on its old philosophical style of thinking based on scholastic "natural law" and replaced it with an attempt to allow the Gospel to interact with the "joys and woes, the griefs and anxieties" of the age. Catholics were told to join in secular public life. It was the beginning of the process of breaking the alliance between Roman Catholicism and socially conservative forces. The fruit of that new openness is evident in today's document.

From the next pope, today's document takes the insight that social concerns cannot simply be about the relationship between individuals or classes. They have to encompass nations too. Economic justice is essential for peace, said Paul VI in Populorum Progressio in 1967. His vision was more utopian. He condemned unbridled capitalist liberalism because it paved the way for a particular type of tyranny. He insisted that free trade was, by itself, no longer adequate for regulating trade between the rich and poor worlds. He wanted an international regulatory body, which prompted the Wall Street Journal to dismiss his encyclical as "warmed-over Marxism" - which is why, perhaps, the English bishops today are less ambitious in considering the Third World, calling more specifically for fewer protectionist tariffs on the goods of poor nations entering the European marketplace.

They appear to have extrapolated from Paul VI in the domestic area, however. The pope had rich and poor nations in mind when he wrote: "When two parties are in very unequal positions, their mutual consent does not alone guarantee a fair contract; the rule of free consent remains subservient to the demands of the natural law." Today's document applies that to modern employment practice insisting that the replacement of collective bargaining with individual contracts can be a serious cause of social injustice.

The document's pronouncements on employment draw on two other papal sources. Relying on the principle of the common good, the bishops criticise unions which direct their strikes at the public rather than their employer. But it is to the present pope they chiefly turn in this area. Work is at the centre of all social issues, wrote John Paul II in Laborem Exercens in 1981; work not only expresses human dignity, it also increases it.

The Polish pontiff, as might be expected, is keen on Solidarity - not just the compatriot trade union of that name but the principle it embodies. Solidarity - the recognition that we are responsible for one another - is, he has written, the foundation of community. It is not a transient feeling but a "firm and persevering determination to commit oneself to the common good." The UK bishops call on Cath-olics to join their appropriate trade union. The recent decline in union membership in Britain is not healthy for society, they say. And the refusal by companies to recognise or to negotiate with unions is wrong. Laws may have to be introduced to force employers who refuse to recognise unions or who refuse to conduct collective bargaining.

Catholic Social Teaching is an area which John Paul II has developed more than any other pope, with five encyclicals on the subject. One of his most distinctive contributions is on the notion that sin can be social as well as personal. It can reside in economic and political structures which force individuals into sin. And we may all be complicit in injustices which at first sight do not appear to be our moral responsibility.

"Those who cause or support evil or who exploit it, or those who are in a position to avoid, eliminate or at least limit certain social evils but who fail to do so out of laziness, fear or the conspiracy of silence, through secret complicity or indifference, or those who take refuge in the supposed impossibility of changing the world and also those who sidestep the effort and sacrifice required" are all culpable, he wrote in Reconciliatio et Paenitenti in 1984. "Obstacles to development," he added in Sollicitudo Rei Socialis in 1987, "have a moral character". These he described, borrowing from the vocabulary of Liberation Theology, as "structures of sin": underdevelopment in the Third World is linked to "super-development" in the "so-called civilisation of consumption and consumerism [in which] one quickly learns that the more one possesses the more one wants."

In the run-up to the British general election the nation's bishops are not reticent about identifying such structural evil. Drawing on the Vatican's worldwide network and diplomatic service, they locate it in unjust trading policies with poor nations, the continuing burden of "unpayable" Third Wold debt and harsh IMF and World Bank structural adjustment programmes which cut health and education provision in Africa and Latin America.

The philosophical framework of the common good, with its pillars of solidarity and subsidiarity (a concept borrowed in recent years by politicians throughout Europe) are tempered by another key principle - the Christian "option for the poor" which insists that preference should always be given to the most vulnerable in society.

Such a framework, the bishops insist, places them above party politics. The Common Good is fundamental to Conservative tradition, concern for poverty is at the heart of Labour's heritage and an emphasis on local democracy is a cherished Liberal Democrat tenet.

And indeed there are some accommodations of more conservative political outlook. In 1991, John Paul II marked the 100th anniversary of the first social encyclical by publishing Centesimus Annus, a document which was much more ambiguous in tone. He did warn yet again of "savage capitalism"and the "idolatry of the market". But this time his criticism was balanced with some adverse remarks about the welfare state - apparently under the influence of the right-wing Catholic philosopher Michael Novak - which the Pope said promoted dependency, sapped people of energy, created bureaucracy and vastly increased public spending.

A similar countervailing tendency is evident in today's UK document. It too contains sections on the importance of wealth creation and the need for bad employers not to be subsidised by the taxpayer through the payment of income support to those not in receipt of a just wage. These sections were apparently strengthened at the insistence of Cardinal Hume, who took advice on the overall document from his brother-in-law, Lord Hunt, the former Cabinet Secretary.

Nor is there any compromise on morality. The bishops draw on the sentiments of the present pope, whose 1993 encyclical Veritatis Splendor warned of the consequences of an alliance between democracy and ethical relativism. Democracy is not enough, the bishops insist. It can produce the tyranny of the majority and the reduction of rights of the minority. To work, democracy needs a system of common values to undergird it. Politics today in Britain "badly needs remoralising".

It is a call to which politicians will be unsure how to respond. The sum of all the bishops' parts does not conform to a creature to be spotted in any of the usual British political fieldguides.

Yet they will have to find a way. Today's document from the Catholic bishops marks a new stage in the growing self-confidence of their church. After generations of anti-Catholic prejudice and association with the special pleading of Irish immigrants it has lost its defensiveness. With the Church of England convulsed in its continuing crisis of confidence, we can only expect to hear more from the Catholic bishops.