We may have a Good Doctor Guide. But what we need is a Bad Doctor Guide - something that will tell us, for example, the name of the surgeon whose death rate for prostate gland surgery is six times the national average, or the orthopaedic unit where one in 10 hip replacements need re-doing after only five years.

The Royal College of Surgeons knows both these names through medical audit, but won't tell. The public, a spokesman recently explained, are not sufficiently 'skilled at epidemiology that they can weigh up all the probabilities in a situation'. And doctors themselves are unlikely to draw attention to a colleague's clinical deficiencies because a combination of Masonic-style secrecy, institutional loyalty and fear means that they, 'and indeed the whole NHS system collude in concealing poor performance'. That's the dismal picture of entrenched mediocrity in British medicine painted by BBC1's Trust Me I'm A Doctor star, Dr Phil Hammond in his new book of the same name, published this week.

He should know. Back in 1992 as a junior doctor with a sideline in stand-up comedy, he made the decision to draw attention to, for the first time, the developing scandal at the Bristol Royal Infirmary's children's surgery unit in his anonymous Private Eye column, Doing the Rounds. During 1992 and 1993, he brought the house down at numerous after-dinner cabarets to medical audiences with jokes about a surgical unit in the South West of England where the mortality rates were so high it was known to staff as The Killing Fields and The Departure Lounge.

Everyone knew about Bristol, Hammond says he was later told - even the Department of Health which carried out an audit of the unit in 1992. But it didn't stop the surgeons concerned from continuing to practise. Nor did it stop cardiologists from continuing to refer.

With the Kennedy enquiry into Bristol about to start and disturbing revelations about the lottery of children's liver surgery uncovered last week, Hammond says it's high time to take a close look at the substandard care we receive from, he estimates, around 1 in 10 of doctors.

One reason for this parlous situation is underfunding and bad management, Hammond argues. For over 10 years, doctors have known that specialist care for cancer and stroke patients brings huge benefits. But there is still no national programme of organised stroke care and one in every four cancer victims is treated by a general surgeon. Treatment of rare diseases can also be appallingly mediocre, he says.

News came last week that nine out of 15 centres in Britain which treat biliary artesia, a condition in babies requiring complex liver surgery, only do one operation a year and these units achieve a success rate that is a quarter that of the best units. The discovery has forced the Department of Health to consider banning all but a handful of surgeons from performing the surgery, and may lead to litigation on behalf of parents whose children received substandard care.

Another example is cleft palate surgery: only one in 10 centres providing cleft lip or palate repair in British hospitals give 'good to excellent' care, according to an independent audit carried out last year. And the average outcome is up to 12 times poorer than the average European unit with 40 per cent of British children left with problems with speech, dental bite or lip appearance after surgery.

The existence of too many general surgeons who are 'less good at admitting their limitations, abandoning their egos and working in specialist teams' lies behind another scandal, unearthed by the Trust Me I'm A Doctor team.

In 1982, Basingstoke surgeon, Bill Heald pioneered a new 'meticulous' technique for treating rectal cancer which cut recurrence rates from an average 35 per cent to between 2 and 6 per cent, and impotence rates by a third. In 1999 the technique, known as Total Mesorectal Excision, has revolutionised rectal cancer care in Europe and America but, says Hammond, it has been largely ignored in the UK.

There's also a salutary warning for hip replacement patients who place their faith in the NHS that their surgeons may well be testing one of scores of new designs for drug companies without mentioning it - even though there are well-established designs with good track records.

Bristol, Hammond believes, will have a major impact on the future of medicine. The Kennedy enquiry will expose 'complicity at all levels - trust, health authority, Royal College, General Medical Council and Department of Health.' The substantial litigation facing the BRI, and at least one other hospital will change attitudes, he says.

To ensure that the best is good enough, says Hammond, 'we need informed, assertive patients'. That may mean questioning the doctor's expertise, if necessary to his or her face - something that is rarely easy.

Take amniocentesis - the test done in pregnancy to ascertain whether a baby has Down's syndrome which involves using a needle to draw off fluid from the placenta. The rate of miscarriage caused by the procedure is said to be between 0.5 and one per cent - except in centres where the needle is manipulated 'blind'. But this is something that happens every day in the UK, due to lack of training and skill in both junior and senior obstetricians. When the procedure is done blind the miscarriage rates rise as high as four per cent - eight times as high as best practice.

And how do you know what sort of amniocentesis you're getting? By popping the question: 'Are you using continuous ultrasound guidance so that the needle tip is always in view?' - and if the answer is no, asking to see someone else. Not easy for a woman 'petrified she might have a baby with a congenital abnormality, lying on her back and facing an obstetrician with a needle', notes Hammond. The Trust Me team has spoken to a health visitor, who as a patient was able to ask this question and was also brave enough to ask to see another doctor after discovering the first one was doing a blind amniocentesis. When she asked the second consultant, who did the procedure properly, why he allowed a colleague in his department to do it blind, he told her he wasn't able to comment. And that's called medical ethics.

• Trust Me (I'm a doctor) by Phil Hammond and Michael Mosley is published this week by Metro Books, price £9.99.