The French National Assembly has passed a controversial bill tightening entry conditions for the relatives of immigrants living in France.
Mr Sarkozy has made immigration one of his signature issues
Under the legislation, the relatives will have to prove they are solvent financially and can speak French.
It also includes plans for DNA testing of foreigners seeking to join family members living in France.
But the new bill has been criticised by some members of President Nicolas Sarkozy's centre-right government.
The legislation would require immigrant family members older than 16 to take a test in their country of origin, demonstrating a good knowledge of French language and values.
Applicants would also have to prove that their family in France could support them and earn at least the minimum wage.
If immigration officials doubt that an applicant is a genuine relative of the person they seek to join, they could be asked to take - and pay for - a DNA test to prove a biological link.
An amendment to the bill on these tests says they will be carried out for a trial period of only two years.
The legislation was "fair" and would provide "tools to fight against illegal immigration", Eric Ciotti, an MP from Mr Sarkozy's centre-right UMP party, told Reuters news agency.
But Foreign Minister Bernard Kouchner, a socialist, and Martin Hirsch, a campaigner for the homeless who joined Mr Sarkozy's government, criticised the measure.
The opposition voted against the bill, which will be debated in the Senate next month.
The UMP and its allies have a majority in both chambers.
Mr Sarkozy has set up deportation quotas, promising to send home 25,000 illegal immigrants this year alone.