The Medical Defence Union has welcomed moves to establish a new body to independently adjudicate on General Medical Council (GMC) cases.
But it claims that the introduction of a civil standard of proof will not improve patient safety, and may undermine confidence in the regulatory system.
Dr Hugh Stewart, the MDU's medico-legal adviser said: "We welcome the fact that the process of deciding whether or not a doctor's fitness to practise is impaired will, in future, be independent of the GMC - passing to the Office of the Health Professions Adjudicator (OHPA).
"Since it sets standards and prosecutes cases, the GMC's independence as an adjudicator may be open to question and we hope that the OHPA will ensure doctors get a fair hearing at the adjudication stage.
"While we support the Government's aims to improve patient safety, and that where concerns about individual doctors exist, they are tackled swiftly, fairly and effectively, we do not believe that all of the changes to professional regulation will achieve this aim.
"In particular, we do not believe it is in the public interest to lower the threshold of proof from the criminal to the civil standard for FTP panel hearings.
"If the civil standard is introduced, it could lead to inconsistent and unfair decisions in many cases, which may result in a greater number of legal challenges, undermining and delaying the regulatory process for doctors and patients alike."