Infertile couples are being misled by some private clinics which offer useless tests to identify the source of their problem, the Royal College of Obstetricians says today.

In a warning to the tens of thousands of couples who seek treatment for infertility, the college says a number of screening tests developed in recent years and offered by clinics are "scientifically unsound".

Many of the tests are promoted on the internet and suggest that the failure to conceive children or experiencing repeated miscarriage may be caused by immunological abnormalities. A review by the college's scientific advisory committee has found that, with one exception, there is no good evidence that immunological abnormalities cause either infertility or miscarriage. The exception is antiphospholipid syndrome which is a recognised cause of miscarriage. It can be treated with aspirin or heparin, the college says.

Causes of infertility may lie with either the male or female partner but in 20 per cent of cases no explanation is found. Recurrent miscarriage may also be unexplained and affected couples often find the lack of explanation adds to their difficulties.

Professor Lesley Regan, who carried out the review, said: "It is clear that the advice given on many sites is strongly influenced by the personal prejudices of doctors practising non-evidence-based medicine."

A spokesman for Alan Beer, who runs clinics in California and London, said: "Dr Beer has been doing this for years and he totally disagrees with the report. He has had amazing success and hundreds of babies have been born as a result of his treatment."