A screening test which can reveal prostate cancer is too unreliable to be recommended to patients, it is claimed.
The PSA test can reveal the presence of cancer
PSA, or prostate specific antigen testing, is often offered to older men as part of private health assessments.
However, a UK expert writing in the British Medical Journal says it should not be widely used as it is not clear whether it actually benefits patients.
Men testing positive do not fare better than those whose cancer is only spotted when symptoms emerge, it is claimed.
The prostate gland is found in men near the bladder, and makes an ingredient of semen.
Prostate cancer is the most common in men, and often, by the time symptoms arise in aggressive cases, it has spread beyond the gland itself.
This makes it far harder to treat successfully.
The PSA blood test looks for a protein produced by prostate cells - higher levels suggest either a benign prostate enlargement, or perhaps the presence of a cancer.
However, it does not confirm cancer - a man needs to have a biopsy operation to make sure - and the test is often wrong.
Another problem is that prostate cancer is often a relatively slow-growing disease of older men - who, if left untreated, would die with the disease rather than of it.
A positive PSA test can mean that many cancers which could easily have been left untreated with no ill effects for the man are removed by surgeons, creating unnecessary risk - and a chance of disabling side-effects such as incontinence and loss of sexual function.
Many experts in the UK are unconvinced that the PSA test is worth giving to apparently healthy men.
However, some firms routinely offer the test to men over 50 years old.
Professor Malcolm Law, from the Wolfson Institute of Preventive Medicine in London, wrote in the BMJ that public health authorities should not advocate tests of "unproven value".
He said: "At present the one certainty about PSA testing is that it causes harm.
"Some men will receive treatment that is unnecessary - and the treatment will cause incontinence, impotence and other complications.
"In one study over two-thirds of men receiving either radical prostatectomy (surgical prostate removal) or radiotherapy were affected."
He is also critical of breast and testicle self-examination advice - suggesting that this advice also leads to unnecessary treatments.
Self-examination advice has now been dropped in favour of breast and testicle "awareness", in which people are urged to be alert for changes, rather than actively seek them out.
Dr Chris Hiley, Head of Policy and Research at The Prostate Cancer Charity, agreed that PSA screening was not worthy of recommendation by doctors.
She said: "We're not in favour of PSA screening.
"We can measure the harm caused by prostate testing - unfortunately we can't measure the benefits.
"Men considering taking a test like this should think very hard and get good advice about whether it is suitable."