Catherine Hakim, a British social scientist and bestselling author who was educated in France, argues that a "sour and rigid English view" of infidelity is condemning millions of people to live frustrated "celibate" lives with their spouses.

In a book bound to provoke controversy, she likens faithful husbands and wives to "caged animals" and argues that they should be free to explore their "wild side" with lovers without the threat of divorce.

Meeting a secret lover for a casual encounter should be as routine as dining out at a restaurant instead of eating at home, she claims.

British couples should take their cue from the French, who she claims are happier and have more stable home lives because of a permissive and "philosophical" approach to adultery.

Husbands in Britain could also learn much from the "experienced libertines" across the Channel whom, she insists, are the "masters of seduction".

Hakim, a former London School of Economics social scientist now based at the Centre for Policy Studies, provoked controversy last year with her book Honey Money, which urged women to exploit their "erotic capital" to get on in life.

In her latest book, The New Rules, she renames adulterous trysts as "parallel relationships" and "playfairs", while rebranding secret lovers as "playmates".

She claims that there is such a thing as a "successful affair" in which both parties are happier but no one gets hurt.

Countries, such as France and other southern European nations, with apparently more accepting attitudes to marital betrayal, also have lower divorce rates, she points out.

Similarly, she lauds Japan with its Geisha traditions and greater acceptance of pornography in contrast to the "killjoys" in Britain and America.

"Sex is no more a moral issue than eating a good meal," she writes.

"The fact that we eat most meals at home with spouses and partners does not preclude eating out in restaurants to sample different cuisines and ambiences, with friends or colleagues.

"Anyone rejecting a fresh approach to marriage and adultery, with a new set of rules to go with it, fails to recognise the benefits of a revitalised sex life outside the home."