The International Helsinki Federation for Human Rights said on Wednesday a proposed new law which would ban Islamic headscarves and other religious insignia in schools would contravene the most basic human rights.
The stinging criticism came after French President Jacques Chirac backed the proposed law because he said France needed to safeguard its secular identity.
But the IHF said wearing the hijab is an essential part of a Muslim woman's religious identity, and the state cannot tell people how to dress unless others' human rights are being violated.
It added banning headscarves would not promote integration and combat "Islamic fundamentalism", but would instead alienate French Muslims.
"For many Muslim women wearing a headscarf is a deeply personal choice and a sign of their religious conviction and has nothing to do with Islamic findamentalism"
The International Helsinki Federation for Human Rights
"For many Muslim women wearing a headscarf is a deeply personal choice and a sign of their religious conviction and has nothing to do with Islamic fundamentalism,' the IHF said in a statement.
"A headscarf ban would automatically but mistakenly stigmatise all Muslim women wearing the headscarf as fundamentalists."
The statement added: "Banning girls and women wearing the headscarf from schools... could lead to numerous girls and women staying out of schools."
Earlier in the day, Jacques Chirac backed last week's findings of France's secularity commission.
"The Islamic veil... the kippa and a cross that is of manifestly excessive dimensions - these have no place in the precincts of state schools. State schools will remain secular," he said.
He said the law should be in effect by the start of the next school year in September 2004.
Chirac says secularism is crucial
to France's national cohesion
"Secularism is one of the great conquests of the Republic. It is an element crucial to our social peace and national cohesion. We cannot let it weaken. We must work to reinforce it."
The headscarf issue has become the focus of a growing debate over how best to integrate France's five million-strong Muslim minority.
Ardent secularists fear the headscarf is an outward sign of a refusal to assimilate fully into French society.
However, many Muslims in France argue the hijab is a religious obligation which is perfectly compatible with France's secular principles.