Checks aimed at identifying poor-performing doctors will do nothing to help find or stop them, according to a poll of more than 5,600 doctors.
More than 80% of hospital doctors and 67% of GPs also pointed to variations in care, saying there are certain doctors they would not want to treat their friends and family.
The survey, by doctors.net.uk as an exclusive for the Press Association, was carried out among more than 4,600 hospital doctors and a further 1,000 GPs.
It was released ahead of the anniversary on Monday of serial killer Harold Shipman's death.
Doctors were asked whether revalidation - the process of appraising doctors - would help identify and deal with those who are unfit to practise. Some 53% of hospitals disagreed it would (33% disagreed and a further 20% strongly disagreed).
Meanwhile, 22% agreed revalidation would help identify and tackle problem doctors, while the rest neither agreed or disagreed or did not know.
Among GPs, 60% disagreed that the plans for revalidation would help to identify and deal with doctors who are not fit to practise (32% disagreed and a further 28% strongly disagreed) while only 16% agreed (15% agreed and a further 1% strongly agreed).
Some 86% of hospital doctors also agreed there are variations in care and that "there are certain doctors that I would not want to treat friends and family".
Of the 86%, 52% agreed and a further 34% strongly agreed. Just 3% disagreed while the rest did not know or neither agreed or disagreed.
The results were similar according to the seniority of the doctor, with 86% of hospital consultants agreeing with the statement compared to 84% of junior doctors.
Among GPs, 67% agreed there are variations and certain doctors they would not want to treat friends and family (50% agreed and a further 17% strongly agreed) while 6% disagreed (including 1% who strongly disagreed).
When asked whether "plans for revalidation will help me maintain a good standard of practice", 33% of hospital doctors agreed they would (30% agreed and a further 3% strongly agreed). Meanwhile, 32% disagreed and a further 23% strongly disagreed. The rest neither disagreed or agreed, or said they did not know.
Among GPs, 46% did not think revalidation would help them maintain a good standard of practice, while only 28% agreed it would.
When quizzed on whether they thought the benefits of revalidation would outweigh the administrative time required for the process, 38% of hospital doctors disagreed they would, while 18% agreed. The rest did not not know or had no opinion either way.
Among GPs, 63% disagreed while 15% agreed.
Dr Tim Ringrose, chief executive of doctors.net.uk, said: "GPs and hospital doctors seek to uphold the highest possible standards in care, and their willingness to be totally frank about variations in quality demonstrates how keen they are to see continual monitoring and improvement.
"However, while revalidation should help to address such concerns, there is widespread scepticism about its effectiveness.
"Many hard-pressed doctors view it as yet another administrative burden. They do not see it as a safety net for identifying any doctors who are not fit to practise or as a benchmark for ensuring that all patients receive the highest possible levels of care and treatment."
Shipman, who was 57 when he died, was jailed for life in January 2000 for murdering 15 patients while working in Hyde, Greater Manchester, and was found hanging in his cell in Wakefield Prison in 2004.
An official report later concluded he killed between 215 and 260 people over a 23-year period.
Shipman's conviction led to intense scrutiny regarding the professional regulation of doctors. A new system of revalidation is now being implemented across the NHS.
Revalidation will require doctors to demonstrate on a regular basis - usually every five years - that they are up to date and fit to practise. Revalidation started in December 2012. The majority of licensed doctors are expected to be revalidated by March 2016.
Licensed doctors will have to revalidate by having regular appraisals with their employer based on core guidance for doctors published by the General Medical Council (GMC).
Dr Mark Porter, chairman of the British Medical Association (BMA), said: "The revalidation system was never designed to catch criminals like Harold Shipman and its introduction was talked about well before his heinous crimes were revealed.
"Instead, revalidation is intended to encourage lifelong learning amongst doctors and lead to a culture of positive professional improvement throughout a medical career.
"Many doctors have been frustrated by the implementation because heavy workload and financial pressures in the NHS leave little time and space for the reflection and quality improvement that revalidation promised.
"The vast majority of doctors in the UK provide excellent clinical care to the millions of patients who are treated by the NHS each year.
"It is the duty of all doctors to be vigilant regarding the standards of healthcare delivered by other professionals in the health service, but we do need to ensure the NHS encourages an open, transparent culture where doctors feel supported and empowered to raise concerns, and ramifications are listened to."
Health minister Dan Poulter said: "Historically, doctors' appraisals in the NHS have been patchy and inconsistent.
"This poll shows that doctors themselves think there are variations in the quality of care and that is why the new system of medical revalidation is so important.
"The UK is leading the world on this - we are the first country to introduce such a rigorous system to regularly make sure doctors are keeping up to date with medical knowledge and skills.
"We are also toughening up checks when hospitals use locum doctors, so patients can be confident in the safety and quality of their care."
Niall Dickson, the GMC's chief executive and registrar, said: "These are very early days of a new system for making sure every doctor in the UK is subject to an annual check and is able to demonstrate that they are practising safely.
"Of course, it can never spot every instance of poor practice, but over time we are confident it will make a difference.
"So far only 12% of doctors have had their licence revalidated by the GMC, yet we know the process has already had a positive impact.
"Employers are taking their responsibilities for ensuring the quality of medical practice more seriously, and we have seen a significant increase in appraisal rates for both hospital doctors and GPs across the country.
"In the last year we have had face-to-face meetings with more than 5,000 doctors to talk specifically about revalidation and to hear first-hand about their experiences - these encounters have been largely positive, although inevitably there will also be some anxiety among some individuals.
"This is not a panacea, but a contribution to patient safety and we will develop the model over time."