The General Medical Council is doing too little to protect patients, the latest report from the Shipman Inquiry has said.
Harold Shipman is believed to have killed at least 215 patients
The report criticises the GMC for "looking after its own" and recommends a radical shake-up in its structure.
The GMC says it is making wholesale changes, but the report said its reforms did not go far enough.
The inquiry was set up in 2001 after GP Harold Shipman's conviction in a bid to prevent such events occurring again.
Dame Janet Smith, who is chairing the inquiry, said that there should no longer be a majority of GMC members elected by doctors.
Change GMC structure to remove medical majority
The GMC to no longer have sole responsibility for assessing doctors' fitness to practise
The GMC to be directly accountable to Parliament
Improvements to the way doctors' performance is assessed
A central NHS database containing information on all doctors
Systems to be in place to allow staff to raise concerns
The 1,300-page report, the fifth the inquiry team has produced, makes over 100 recommendations.
Dame Janet said: "I cannot guarantee that, if all my recommendations are implemented, it will be impossible for a doctor who is determined to kill a patient to do so without detection.
"But I believe that, if my recommendations are introduced, the deterrent effect will be considerable, and the chances of a doctor such as Shipman escaping detection will be very much reduced."
In the report, Dame Janet accepted that the GMC had introduced changes to the way it works in light of the Shipman case.
Reforms already introduced include a speeded-up complaints process and ensuring there are 14 lay people on the council's 35-member governing body.
But Dame Janet said: "I am by no means convinced that the new GMC procedures will adequately protect patients from dysfunctional or under-performing doctors.
"I have concluded there has not yet been the change of culture within the GMC that will ensure that patient protection is given the priority it deserves."
Dame Janet said she believed the GMC should be given the opportunity to put its house in order.
But she said its role in both investigating and punishing doctors, its fitness to practise procedures, should be split up.
Doctors should instead be disciplined by an independent body.
She also called for this to be reviewed in three to four years, with the potential for fitness to practise to be taken away from the GMC altogether if it was found to be wanting.
However Dame Janet said the GMC was not at fault when it decided not to discipline Shipman after his conviction for of obtaining pethidine by deception in 1976, allowing him to return to unrestricted practise.
The GMC said it was pleased to have been found not to have been at fault in the way it dealt with Harold Shipman.
But it defended its current reforms. Sir Graham Catto, president of the GMC, said: "I am certainly not complacent. I have introduced the most radical reform programme for medical regulation, not just in this country, but in any country."
The GMC added that the public was involved in every stage of our processes, and there would be even greater involvement in the future.
In a statement, the GMC added: "We are making every effort to make our own procedures accessible, streamlined and transparent, but we have long called for a 'single portal' that could be the confidential first port of call for people with concerns.
"We welcome Dame Janet's support for this proposal.
The report also makes many recommendations for how the NHS should change.
It calls for a central database to be established containing information about all every doctor working in the UK which would be accessible to both patients and NHS bodies.
She also criticised plans for a new system of revalidation - which will involve regularly checking doctors competency to practise - which are currently being finalised - because doctors would not face objective tests which would allow their fitness to practise to be properly evaluated.
Responding to the report, Health Secretary John Reid accepted that more work was needed to reform the GMC.
He said: "We have been working hard with the medical profession and others to strengthen the systems, rules and regulations that govern the medical profession.
"Standards of behaviour must be high and action against those who fail to maintain those standards must be timely, firm and fair.
"Nothing should be higher than the protection of patients."
Harold Shipman was convicted of 15 murders in 2000. But Dame Janet's inquiry concluded it was likely he had killed at least 200 more patients during his career.
The former Hyde GP was found hanged in his cell in Wakefield Prison in January this year.
The government said on Thursday it would ask the Healthcare Commission to oversee how NHS bodies manage the use of controlled drugs after the Inquiry's Fourth Report recommended the establishment of a drugs inspectorate to prevent doctors stockpiling drugs as Shipman did.