French women not only earn less than men doing the same job but also considerably less if they are married or living with their male partners, reports The Guardian.
A study by France's national statistics institute Insee found that three quarters of the country's women who had a revenue and were in a relationship earned an average of 42% less than their husbands or boyfriends.
The difference between single men and women is only 9%, said researchers.
Insee carried out the study of France's estimated 10 million heterosexual couples aged between 20 and 59.
In 44% of couples, both partners worked full-time; in 20% the men worked full-time and the woman part-time. In other cases, the woman was unemployed or retired.
In 2011 the average salary of the woman in a couple was €16,700 compared with €29,000 earned by her partner. Only a quarter of full-time working women earned more than their male partners.
With the arrival of children the figures shift as Insee says many women sacrifice their careers to bring up their offspring.
"The difference in income at the heart of couples is greater when there are children and when the couple is married, and less when the couple is younger and more educated," says the report.
Researchers found that married women appeared to earn less than those who were living with their partners or in civil relationships.
"It is possible that the status of being married reinforces an idea of stability for the couple involved, making such inequalities in revenues less problematic when there is a pooling of resources," says the report.
Read more of this report from The Guardian.