Ten years ago, when emigration rather than immigration was still the hot topic of debate in Ireland, the historian Joe Lee ventured an explanation for the peculiar Irish phenomenon of begrudgery.

In his Ireland 1912-1985, Prof Lee argued persuasively that the culture of begrudgery resulted from a perception that economic advancement was a zero-sum game. Prosperity, success and prestige, he wrote, were seen as a cake of limited size.

"The size of that cake was more or less fixed in more or less stagnating communities and in small institutions. In a stunted society, one man's gain did tend to be another man's loss. Winners could flourish only at the expense of losers. Status depended not only on rising oneself but on preventing others from rising. For many, keeping the other fellow down offered the surest protection of their own position."

Resentment about immigration may derive from pure racism or from the manipulation of xenophobia for political ends. In Ireland at the moment, however, much of it derives from this kind of fairly rational begrudgery.

As the economy has expanded beyond recognition over the last decade, most of the population has left behind the perception that the cake is of a finite size. Those in the economic mainstream have seen the cake grow before their eyes and have learned that a slice for someone else is not necessarily taken from their own mouths.

For a significant section of the population, however, the cake still seems all too limited. For the long-term unemployed, their families, and the communities in which they are concentrated, nothing has happened to fundamentally alter the old perception that if someone else is rising, it must at their expense. If anything, that perception has been strengthened by the evidence that many of those who gained most in recent years did in fact rise at the expense of others.

When this mentality survives, immigrants are bound to be resented. The reality may be that immigration actually increases the size of the cake, that their energies, talents and resources fuel economic growth. Economists may be able to show that substantial inward migration over the next decade is vital for the sustaining of the Irish boom.

The evidence from every developed country may be that immigration is a boon, not a burden. But in order to see this, you have to have stopped seeing the world as a place in which one person's gain is another's loss. And for parts of the Irish population, there has been no persuasive reason to stop seeing the world in that way.

It is not, of course, that the current shambles in immigration policy is the fault of the long-term unemployed. The chaos has been created by the failure of the State to develop any coherent strategy for legal economic migration. That failure has forced economic migrants to claim that they are asylum-seekers, with disastrous consequences for those who really are in need of asylum and to whom the State has moral and legal obligations that are not being met.

Public debate has been distorted by a rhetorical opposition between "genuine asylum-seekers" and "economic migrants" in which the latter term - an accurate description, as it happens, of something close to a majority of those born in Ireland in the last 150 years - has become a term of abuse. When the State effectively implies that economic migration is essentially a criminal activity, is it any wonder that many citizens find it hard to see it for what it is, the literal and metaphorical enrichment of Irish society?

A key factor, too, has been the leading role of the Department of Justice, the arm of the State whose natural tendency is to see itself as the doughty defender of order against myriad threats. Departments of justice everywhere naturally develop a siege mentality. And the Irish Department has a particular and deep-rooted culture of xenophobia.

The most influential figure in the creation of the modern Department's ethos was Peter Berry, who remained as secretary well into the 1970s. Berry summarised Irish immigration policy in 1953, just eight years after the end of the Holocaust, by noting that "the question of admission of aliens of Jewish blood presents a special problem and the alien laws have been administered less liberally in their case."

But even if, after the debates of this week, a rational immigration policy does emerge and official paranoia is overcome, resentment is likely to continue among those who, however misguidedly, see immigrants as a threat to their own survival and status. And it must be acknowledged that the fears of many at the bottom of the heap are not entirely irrational.

There are reasonable grounds to suspect that for the some within the policy-making establishment, immigration is seen, not as a supplement to a fully engaged Irish workforce but as an alternative to the integration of those who are currently unemployed into the productive economy.

It may be timely to look at things from the point of view of those who are on the dole. Just a few years ago, the economic buzz-words were "the end of full employment". Those who lost their jobs in the 1980s were told that they would never work again.

Especially for those in older age groups, this perception was made official by the institution of the so-called Pre-Retirement Allowance for unemployed people over 55. They did not have to sign on or be available for work. They were, to all intents and purposes, given a cheque in the post that would maintain them in permanent unemployment. Many unemployed people got the message and switched off from the productive economy.

Suddenly, in the last year, while there are still (depending on which set of figures is used) around 150,000 people on the dole, the State has been declaring the battle against unemployment won and proclaiming the achievement of virtually full employment. At the same time, words like "unemployable" have been attached with increasing frequency to those who are still out of work.

And with this week's announcement of a Public Accounts Committee investigation into discrepancies in the unemployment figures, with the implication that huge numbers of those who remain on the dole may be fraudsters as well, the stigma of being out of a job is increasing.

IT should not be hard to understand why such people might begin to suspect that their productive potential has been tacitly written off and that they will be replaced in the future workforce by immigrants. It does not help, either, that the number of immigrants posited by economists as being required in the Irish workforce in coming years (160,000) is remarkably similar to the number of Irish people currently unemployed.

Given the likelihood that immigrants will tend to be concentrated, at least initially, in areas of high unemployment, the potential for resentment is obvious. And so is the temptation for ambitious politicians to fuel that resentment with a few carefully coded phrases.

If Ireland is to avoid the kind of neofascist politics that have disfigured much of the rest of Europe, it is essential that those at the bottom of the heap are given reasons to feel that the cake is not of fixed size and that a gain for a migrant worker is not a loss for the Irish poor.

Immigration policy, in other words, must not be formulated in isolation from social policy. The arrival of new workers has to go hand-in-hand with the regeneration of old ones. If it does, racism is no more inevitable than unemployment.