PARIS (AFP) - French Prime Minister Manuel Valls created a stir on Thursday when he called for a "settlement policy" in France to fight against the "ghettoisation" of neighbourhoods with strong immigrant populations.

Although many were left scratching their heads as to the exact meaning of the premier's words, it is not the first time that he has raised uncomfortable issues in the aftermath of the deadly Paris attacks earlier this month, determined to highlight inequalities in society he believes are partly to blame for the violence.

On Tuesday, he said parts of France were riddled with "territorial, social and ethnic apartheid".

Valls put forward the idea of a "settlement policy", without giving further details of what this would entail.

France is notorious for its "banlieues", or out-of-town areas where low-income residents, often from immigrant families, live against a background of high unemployment, discrimination and simmering tensions.

"I can't stand to see this confinement... that in schools you only find students from poor families, who often have just one parent, all from immigrant families who have the same cultures and the same religion," he said.

"How can we possibly manage?"

Analysts hurriedly tried to decipher what he meant.

"It's about how to impose social diversity and to avoid social categories from grouping together," said Marion Carrel, a sociologist at Lille 3 University.

"It's about deciding to allocate social housing to specific types of applicants, and therefore trying to mix (people) together along social criteria, and also ethnic criteria, even if that is prohibited by law.

"It's a big debate among sociologists. Some say social diversity must not be imposed, it's violent, it means dispersing the poor and people don't necessarily want to live side by side."

Throughout his political career, the popular Valls has never been far from controversy.

In 2009, when he was still mayor of the Paris suburb of Evry, he created a stir when he was caught on camera at a local garage-sale jokingly saying it would be good to add a few more white people to the mix.

At the time, he defended his remarks by saying he wanted to fight against ghettos.

"What's a ghetto? We put the poorest people, often - but not only - immigrants, in the same towns, in the same neighbourhoods, in the same stairwells, in the same schools," he had said in 2009 in comments that strongly echoed his Thursday remarks.