Announcing plans for a French debate on national identity, France's immigration minister, Eric Besson, underlined the thinking behind the project. "We should never have abandoned to the Front National (FN) a certain number of values that belong to our Republican heritage," he said, before expressing his desire for "the political death" of Jean-Marie Le Pen's party.

In this sense, with regional elections due in March, the debate follows an established pattern whereby mainstream parties of both left and right attempt to establish their get-tough credentials on immigration in the hope of winning over voters attracted by the FN. Midway through his presidency, and with its popularity fading, the president, Nicolas Sarkozy, is therefore returning to the issue that established him as an international figure in 2005, when his attacks on the "rabble" that inhabit France's impoverished suburbs sparked a three-week urban uprising during his tenure as interior minister.

What are we to expect from this discussion? The early signs are not promising. When Sarkozy set up a ministry of immigration and national identity following his election in 2007 the message seemed clear: "French" values were threatened by its immigrant population. Last summer he used a historic address to both houses of parliament to launch an attack on the wearing of the burka – no longer welcome, he claimed, on French soil.

During the 2007 campaign Sarkozy counterposed the myth of the "one and indivisible nation" to the threat posed to the republic by ethnic or religious "communitarianism". The republican model of integration prioritises the affiliation of French citizens to the state – and its official values of liberty, equality and fraternity – above other affiliations based on ethnicity or community. But assumptions that this insulates France against the kind of segregation that produces urban ghettos have been upset by studies indicating that the extent of social polarisation in France bears comparison with the US.

Research by the economist Eric Maurin also shows that France is not becoming more segregated – the situation has been more or less static for the past two decades – instead it is the perception of segregation that has increased. Yet the focus on immigration in general – and Islam in particular – as divisive elements in French society prevents an understanding of why this polarisation occurs. At one extreme those who find themselves concentrated in the poorest areas of France do so not out of choice, but through ethnicity and income. Neither Islam nor "ethnic communitarianism" are responsible for such divisions: they are the product of social deprivation and racism. At the other extreme, however, is a section of society that wilfully separates itself from the rest of France. The top 10% of earners choose to live in the most segregated areas of the country, well-heeled districts like Neuilly and St-Cloud on the outskirts of Paris. It is they who have created what Maurin calls "the bourgeois ghetto".

If the present debate is to reassert the historic republican values of liberty, equality and fraternity then government priorities will need to be overturned. The targeting of "illegal" immigrants – Besson aims to deport 27,000 people this year, more than double 2002 levels – focuses attention on a tiny proportion of the population. Likewise, high-profile campaigns to impose a republican dress code on Muslims are a distraction from more fundamental divisions shaping French society, divisions determined less by Religion than by poverty, racism and inequality. In France, as in Britain, if debates on citizenship are to involve denouncing the extreme right while pandering to its bugbears, they will only obscure the real issues – and in so doing become part of the problem.