One of the delights of English life is watching our aging prince scrapping with doctors over integrated, complementary, alternative, or quack medicine (choose the adjective to suit your prejudices). The doctors (most of them fellows of some royal college or another) are incensed by the prince's enthusiasm for the unorthodox - and so lash out whenever he opines on the subject. The media love the battle - and so again and again we have debates over the place of complementary medicine.

This time some senior doctors have pre-empted one of the prince's speeches by writing to primary care and acute trusts asking them not to fund complementary treatments unless they are supported by solid evidence. The appeal is timely when so many of the trusts have financial deficits.

One way to divide medicine is into orthodox and complementary, but another is into those interventions (both diagnostic and treatment) supported by evidence and those that are not. The letter-writing doctors are quite happy for trusts to pay for complementary treatments that are supported by good evidence - acupuncture for pain relief, for example. The doctors are silent on what to do about orthodox interventions that lack evidence - and there's a problem.

The US congressional report some years back estimated that only 15% of orthodox treatments are supported by solid evidence. Various studies have looked at patients in medical wards and suggested that about two-thirds of the treatments they receive are supported by evidence. The difference in the figures is explained by patients in the wards receiving common treatments, most of which are supported by evidence. Many of the 85% of treatments lacking evidence are rare.

The letter was organised by Professor Michael Baum, a famous old bruiser and opponent of complementary medicine. He is a surgeon, and surgery is the branch of medicine that has the weakest evidence base. The history of surgery is a history of mutilating operations that did far more harm than good - including hemicorporectomy (removing the lower half of the body in patients with bladder cancer). Baum is a breast surgeon, and his colleagues were until very recently performing radical mastectomies (removing the breast, the chest muscles, clearing the armpit, and more) despite evidence that a lumpectomy (simply removing the cancer) was just as effective.

Like most people in their 50s I had my tonsils removed as a child - despite no evidence of benefit, and the operation is hardly used now. When my son was born in 1982 my wife was given an enema and had her pubic hair shaved, both interventions entirely unsupported by evidence. If she hadn't had a caesarean section (which itself is done far more commonly than evidence supports) then she might well have been given an episiotomy, another treatment that causes more harm than good.

And when it comes to diagnostic tests evidence is almost wholly lacking. Every year tens of millions of X-rays and blood tests are performed that have no chance of doing good and yet have some potential for harm.

So is what's sauce for the goose also sauce for the gander? Should primary care and acute trusts stop orthodox interventions unsupported by evidence. If they do then the NHS's financial problems will be solved overnight - and a lot of doctors will have time on their hands.

One snag with such a step is that there is a world of difference between lack of evidence and evidence of lack of effectiveness. Many of orthodox medicine's interventions simply lack evidence: there isn't strong evidence that they don't work. But the same is true of complementary medicine.

Yet another snag is that most research findings are false - but that's for another blog.