The controversial measure, which critics say is racist and which sparked large street protests in Paris last weekend, passed by 282 votes to 235 in the lower chamber of parliament, the National Assembly, and by 185 votes to 136 in the upper chamber, the Senate.

The immigration bill originally included an amendment that would have imposed compulsory genetic testing to verify the bloodlines of would-be immigrants who want to join family members already living in France.

The amendment was watered down to make the DNA tests voluntary following an uproar among politicians (even within President Sarkozy's ruling UMP party), intellectuals and immigrant groups that the tests were discriminatory and ran contrary to France's humanitarian values and principles.

The tests, which will be introduced for an 18-month trial period, will now be based on the mother to avoid paternity disputes, and they will be paid for by the state rather than by immigrants themselves. They are meant to be carried out in cases where family records in the immigrant's home country are generally unreliable.

"A day of shame"

The tests still remain deeply controversial, with critics attacking them as racist and for stirring up memories of the ugliest period of modern French history.

"This day will remain a day of shame," the rights group the Movement Against Racism and for Friendship Between People, or MRAP, said in a statement after the measure was passed.

The group compared the DNA tests to anti-Jewish discrimination under the Vichy government, which collaborated with Nazi Germany.

"It will be the second time in France that biology will dictate the law for racist discriminatory aims," MRAP said.

The measure has triggered unease because it challenges the notion of family in French law based on recognition of a child as one's own, not on blood.

"This law violates the fundamental principles of the Republic which do not define family and affiliation by biology," said Arnaud Montebourg of the opposition Socialists.

Test used in 11 EU nations

The DNA testing technique, which is widely used on criminals, builds on Sarkozy's campaign promise to toughen immigration rules. Its supporters say it will help speed up the process for genuine applicants and they cite similar laws in other European countries.

"This DNA test exists in 11 countries in Europe -- including some socialist ones, like Great Britain," President Sarkozy said in a recent television interview.

"How is that it doesn't pose a problem in these countries, but it creates a debate here?"