Doctors will have to show they are fit to practice once every five years under plans to be published by Chief Medical Officer Liam Donaldson on Wednesday.

Doctors falling below standard face the risk of removal from the medical register unless they can show improvements.

The government outlined the proposals last year as part of measures to help restore public trust and confidence in the profession after the case of serial killer Dr Harold Shipman.

At present doctors can only be debarred if complaints about their conduct or medical practice are upheld by regulators at the General Medical Council.

Most doctors already undergo annual peer reviews of their performance, looking at factors such as their prescribing habits and how up to date they are on the latest medical advice and research.

The new scheme will build on this and lead to doctors being recertified every five years.

"There hasn't been that process before," said a Department of Health spokeswoman. "Once someone was certified they could be a doctor for 50 years, the way the current system works."

Shipman managed to kill an estimated 250 patients between 1972 and 1988 without being challenged by a system that was deemed to be stacked in favour of the GP rather than the patient.

But British Medical Association Chairman Hamish Meldrum told BBC radio it would be wrong to think the new system was being introduced just to catch another Shipman.

"Shipman ... was not necessarily a badly performing doctor in terms of his clinical practice not being good - he was a murderer."

"We are not devising system purely to pick up murderers, we are trying to do a system that for the majority of doctors helps them to improve their practice."