Police held Georges Tron, formerly a junior civil service minister, for questioning in the course of their investigations into accusations that he sexually harassed two women who worked in the town hall where he is mayor.
"Mr Tron was placed in custody on Monday at 2:00 pm (1200 GMT)" in Versailles, west of Paris, the lawyer Olivier Schnerb told AFP. "He is currently being questioned."
Tron's resignation from the government on May 29 came amid a wave of soul-searching over sex and secrecy in public life after the French IMF chief Dominique Strauss-Kahn's arrest in New York on sex crime charges.
Strauss-Kahn has since resigned.
Tron has not yet been charged in his case. He has said he will prove his innocence after prosecutors opened a preliminary investigation into accusations of sexual aggression and rape.
He alleged his political rivals were trying to gain momentum from the arrest of Strauss-Kahn.