The British Medical Association (BMA) has attacked the government's plans to change the way doctors are regulated.
The Health and Social Care Bill was announced in the Queen's Speech and seeks to strengthen the way the medical profession is monitored.
Regulatory bodies will be required to use the lower, civil standard of proof which uses the balance of probabilities, rather than the current criminal measure of beyond reasonable doubt.
Healthcare organisations will also be compelled to appoint a "responsible officer" to work with the General Medical Council (GMC) on cases of poor performance by doctors.
But Dr Hamish Meldrum, chairman of council at the BMA, said: "The BMA is keen to ensure that patients are protected from the small minority of doctors who represent a threat to patients.
"However, this will not be achieved by abandoning the criminal standard of proof. The best protection of the public will be achieved by a system that commands the confidence of the profession and will encourage doctors to speak about problems with their own practice, or that of colleagues. We urge the government to think again.
"If a doctor is at risk of losing their livelihood then surely nothing less than the current criminal standard of proof will do. The BMA will continue to lobby very hard to maintain this."