An alliance of Tunisian human rights groups on Monday called on authorities to scrap a 1973 decree that bans Muslim women from marrying non-Muslims.
The alliance of some 60 groups signed a statement calling for the decree to be revoked, saying it undermines "a fundamental human right: which is the right to choose a spouse".
Sana Ben Achour, president of the Beity association, told a news conference "it is inadmissible today for a simple decree, which has almost no judicial value... to command the lives of thousands".
The decree issued in 1973 by the justice ministry stipulates that a non-Muslim man who wishes to marry a Tunisia woman must convert to Islam and submit a certificate of his conversion as proof.
Wahid Ferchichi, of the Adli association for the defence of individual liberties, said the decree violates Tunisia's constitution which promotes equality between all citizens, regardless of gender.
The coalition said it would mount a campaign to mobilise public opinion and seek meetings with the ministers of justice, interior and the head of government, hoping the decree will be scrapped by November.
Tunisia is viewed as being ahead of most Arab countries on women's rights.
The North African country and birthplace of Arab Spring protests that ousted several regional autocratic, adopted a new constitution in 2014 which guarantees equality between men and women.
Article 21 of the constitution states: "All citizens, male and female, have equal rights and duties, and are equal before the law without any discrimination."
But discrimination against women in Tunisia remains rife, particularly in matters of inheritance and the country's Code of Personal Status designates the man as the head of a family.