In an interview with the French daily Le Figaro published on 15 March, Valls said that around 20,000 Roma migrants from Bulgaria and Romania living in some 400 camps had no interest in integrating into French society.
This, he said, was "for cultural reasons or because they are in the hands of begging or prostitution networks."
Valls, a firebrand Socialist who has continued the much criticised repatriation policies of the previous conservative French government, has defended police raids to break up Roma camps near Paris, Lyon and Lille on health and safety grounds.
The activist group Roma Voice ("Voix des Roms") said Valls's comments were "concentrated lies" designed to smear the entire community.
"This interview is a very bad sign," the organisation said in a statement. "It signals a hardening of a policy that has been in place since 2003, when [former President] Nicolas Sarkozy became interior minister," it stated.
Considering a complaint under French law, Roma Voice said they would be reporting Valls' latest comments to the European Commission, which has questioned the legality of France's policy of systematically dismantling illegal camps and repatriating Roma to Bulgaria and Romania.
The expulsions of Roma immigrants to their countries of origin “have never been a solution” to the problem, the NGO adds.
France and Romania signed a deal on the voluntary repatriation of Roma last September.