A survey by one of France's oldest and most reputable polling and market research organisations has challenged the myth of the French lover.
More than three-quarters of Gallic couples have bad sex lives, the Institute for Public Opinion found.
More than one in three women said they had used excuses such as headaches, tiredness or children being nearby to get out of having sex.
Nearly one in six men said they had also made similar excuses.
France has long enjoyed a reputation for romance and the French have traditionally thought of themselves as great lovers, more amorous and flirtatious than most other Europeans, especially the British, the BBC's David Chazan reports from Paris.
But the survey of more than 1,000 French adults, who answered revealing questions about their sex lives, suggests the nation that gave its name to the French kiss could be suffering a loss of libido, he says.
However, help may be at hand, our correspondent adds. The pharmaceutical corporation which commissioned the survey says it is going to launch an information campaign this month for French couples who want to improve their sex lives.