Christiane Taubira made the comment as Parliament began debating a controversial bill to extend rights to same-sex couples, France 24 reported.
"We want to know: what will the marriage of homosexual couples take away from heterosexual couples?" Taubira asked.
Several lawmakers could be heard replying "nothing."
"We are proud of what we are doing," she went on to say.
Polls suggest that some two-thirds of voters in France support gay marriage but conservatives and the Catholic Church are against it.
The debate in Parliament that began Tuesday is expected to continue until Feb. 10. Voting on the measure is set for two days later.
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