A German couple who went to a fertility clinic after eight years of marriage have found out why they are still childless - they weren't having sex.

The University Clinic of Lubek said they had never heard of a case like it after examining the couple who went to see them last month for fertility tests.

Doctors subjected them to a series of examinations and found they were both apparently fertile, and should have had no trouble conceiving.

A clinic spokesman said: "When we asked them how often they had had sex, they looked blank, and said: "What do you mean?"

"We are not talking retarded people here, but a couple who were brought up in a religious environment who were simply unaware, after eight years of marriage, of the physical requirements necessary to procreate."

The 30-year-old wife and her 36-year-old husband are now being given sex therapy lessons while the university clinic undertakes a study to try to find out if there are more couples with a similar lack of sex education.