Ms Dati, 43, gave birth to a girl by Caesarean section on 2 January
French Justice Minister Rachida Dati has come under fire from women's groups for returning to work just five days after giving birth.
Ms Dati attended a cabinet meeting on Wednesday, hours after leaving a Paris clinic with her new daughter, Zohra.
Activists said the move set a bad example for women, and put pressure on new mothers to return to work quickly.
Ms Dati, who gave birth by Caesarean on 2 January, told reporters she felt fine on her first day back at work.
"This is scandalous," Maya Sturduts from the National Collective for the Rights of Women told AFP news agency.
"Employers can now use this to put pressure on women," she said, especially during the current economic crisis when many companies are looking to reduce the number of staff.
Women in France are guaranteed by law 16 weeks of paid maternity leave, but the French labour code does not apply to ministers like Ms Dati.
Woman's rights activist Florence Montreynaud compared Ms Dati to working women in the 1920s who "gave birth in the factories" and lamented that her decision would exacerbate the divide between "superwomen and wimps" in the workforce.
But a French medical expert insisted there were no ill effects from a quick return to work.
"Pregnancy is not an illness," said Georges-Fabrice Blum, vice- president of the French gynaecologists' association.
Dr Blum said Caesarean sections "are a lot less debilitating nowadays in terms of returning to work" and that much of the pain and discomfort can subside the day after the operation.
Still he recommended rest for a period of three weeks to a month.
Marie-Pierre Martinez, the secretary general of the Planned Parenthood association, said Ms Dati "had no choice" but to go back to work to defend her standing in France's male-dominated politics.
President Sarkozy paid tribute to the "young mother" in the cabinet meeting
Ms Dati's diary for the week is full, the AP news agency reported.
Ms Dati shot to prominence in 2007, when she became the first politician of north African origin named to a senior French government post.
The 43-year-old first-time mother, who is single, has kept the father's identity under wraps, telling reporters she had "a complicated private life" and sparking an intense guessing game in the French press.
Government spokesman Luc Chatel told reporters: "Rachida has always said that to be a mother was the greatest of happinesses, but at the same time that she had important duties that she would continue to fulfil."
President Nicolas Sarkozy paid a warm tribute to the "young mother" during the cabinet meeting.