Amnesty says a high number of complaints are closed without a trial
The human rights group Amnesty International has accused the French authorities of failing to investigate alleged violence by security forces.
Allegations of beatings, and even unlawful killings, were rarely looked into and those responsible seldom brought to justice, Amnesty said.
In a report, it cited cases of abuse, many involving ethnic minorities and foreign nationals living in France.
French officials denied that any degree of police violence was being condoned.
David Diaz-Jogeix, the deputy director of Amnesty International's Europe and Central Asia programme said: "In a climate where police abuse can go unchecked, the de facto impunity of law enforcement officials in France is unacceptable."
"Victims, many of whom are French citizens from an ethnic minority or foreign nationals, are all too often left without justice."
Amnesty acknowledged that "not every complaint made against the police has merit", but added that the discrepancy between the number of complaints made and the number of disciplinary sanctions "raises questions about the thoroughness and impartiality of the investigations".
Amnesty said French officials had not acted on recommendations the human rights group had made in a 2005 report into abuse.
Amnesty said in its latest report that "according to limited information" in 2005, there were 663 complaints resulting in 16 dismissals.
The following year 639 allegations were made and eight police officers dismissed as a result of investigations.
A high number of complaints against law enforcement officials were closed by the prosecutor without reaching trial, the report said.
It recommended that an independent police complaints commission be established.
Guillaume Didier, a spokesperson for the French justice ministry, rejected the accusation.
"There is no tolerance for police violence," he told the AFP news agency.
"There are systematic criminal inquiries. Police officers have neither more nor fewer rights than other defendants."
The interior ministry said: "No police officer is above the law."
The National Union of Police Officers defended its members, saying: "There is no unlawful violence... we obey the rules of ethics and those of the code of criminal procedure."