Many French city suburbs are becoming ethnic ghettoes, a report has warned.
Deprivation has led to ghettoes forming in Paris and elsewhere
The study by the French domestic intelligence services found many areas were populated by poor, young French of north African immigrant backgrounds.
The report, leaked to Le Monde newspaper, found at least half of the 630 suburbs it looked at had already become separate ethnic communities.
The report warned the ghettoes, cut off from mainstream French society, could encourage radical Islam to take root.
The intelligence service report deals with an extremely sensitive issue for France: just how bad the sense of alienation has become in the suburbs, among the French-born children of north African immigrant background.
The report - given to the interior minister, Dominique de Villepin - concludes that the situation is actually worse than previously thought.
Of the suburbs studied, the report says at least half could already be called ghettoes, whose inhabitants felt rejected by, and were in turn rejecting, mainstream French society.
The areas studied were chosen because they already had problems with unemployment, crime and violence, had a high proportion of immigrant families - some still practising polygamy - plus a growing number of Islamic prayer rooms as well as frequent anti-Western and anti-Semitic graffiti.
The intelligence services noted that many families of immigrant origin were rejecting French values and even the French language, following instead more traditional ways of life associated with their ethnic origin - including an increasing religious radicalisation among young Muslims, and a backlash against young Muslim women who wore Western clothing.
Better-off families, mainly those of white European origin, were leaving such suburbs, creating an even greater sense of isolation.
The report's conclusions will worry the government, although they are not entirely unexpected.
For decades, France had hoped that its immigrants and their children would simply integrate into secular French society.
Instead, it seems, the opposite has been happening, with the divide becoming ever greater.
France's new law, banning the Islamic headscarf from state schools, had already provoked a national debate on integration.
In an attempt to solve the problems of France's city suburbs, the government has proposed a five-year plan to improve social cohesion - although, as the newspaper Le Monde concludes, it will be a race against time.