* Hollande's left-wing allies outraged by Valls' comments
* Government defends Roma policy as "firmness and humanity"
* Roma row seen major theme in 2014 municipal elections
By Mark John
PARIS, Sept 29 (Reuters) - President Francois Hollande is battling to heal a rift in his ruling coalition over treatment of France's Roma population after his interior minister said most of them should leave France.
Manuel Valls enraged left-wingers in Hollande's government this week by arguing that the vast majority of 20,000 Roma living in makeshift camps outside French cities could never be integrated into society and so should be "taken back to the border" for transfer back to Romania and Bulgaria.
The remarks, widely supported by the public, brought a quick rebuke from European Union authorities which recalled that France was bound by rules on freedom of movement of EU citizens, while human rights groups have warned the comments could stir ethnic hatred.
Hollande's decision to back Valls, whose tough talk on law and order has made him France's most popular minister, has added to discontent among leaders of the French left already dismayed by new public spending curbs aimed at slashing France's deficit.
Housing Minister Cecile Duflot of the ecologist Greens accused Valls of betraying the values of the French Republic and urged Hollande to "heal the wounds" caused by the remarks - an implicit call for him to reprimand his interior minister.
"Until Francois Hollande tells Valls his job is to bring people together rather than to provoke them, it is just not on," Marie-Noelle Lienemann, a leader of the left-leaning faction in Hollande's broad-based Socialist Party, told reporters.
"I think this is weakening Hollande," she said of the impact of the dispute on Hollande's leadership. The president's popularity ratings have already hit a new low of 23 percent in a survey released this week that showed dissatisfaction with his handling of the economy.
"KNEE-JERK REACTION"
Around 10-12 million Roma are spread throughout Europe, according to EU estimates. Countries such as France, Spain and Germany have long struggled to deal with tensions between them and local communities.
Roma is an umbrella term which EU authorities use to refer to semi-nomadic groups including Manouches and Sinti and which number around 300,000 in France - most of them French citizens.
The current row focuses on the much smaller number of Roma immigrants from Romania and Bulgaria housed in some 400 camps on the outskirts of Paris, Lyon, Marseille, Lille and elsewhere.
The far-right National Front has made the issue a top campaign theme for March's municipal elections, warning of a new influx of immigrants when current restrictions on the movement of Romanian and Bulgarian citizens in the EU expire in January.