A new bill cracking down on dodgy health practitioners, including gay conversion therapists, will be introduced to the Victorian Parliament.

Under the legislation, Victoria's Health Services Commissioner will be replaced with a new Health Complaints Commissioner who will be given greater powers to investigate unregistered doctors, dentists and other health service providers.

Victorian Health Minister Jill Hennessy said the new commissioner would crack down on providers currently not covered by state or federal law.

"We've had a number of challenges in terms of the sorts of services people have been provided and no legislative tools to really respond to it," she said.

"An example of some of the challenges we've seen in recent times - we've seen gay conversion therapists out there strutting their wares, we've seen unethical representations about treatments claimed to cure cancer that we know don't work.

"We've had things like fake gynaecologists and unregistered dentists, but because they were beyond the national laws and the state laws had no power, we're filling that gap with some pretty tough new powers."

Ms Hennessy said the new commissioner would not have to wait until a patient had made a complaint.

"For example, we became aware a certain provider was offering ketamine treatments, which is commonly known as a party drug, for treatment of depressive illnesses," she said.

"Because no one who was purchasing ketamine came and complained to the Health Services Commissioner, there was no grounds to investigate it."

LGBT rights groups have been calling for a ban on gay conversion therapists in Australia since a bill was put before the US Congress to outlaw the practice last year.

Ms Hennessy said the new commissioner would also have the power to investigate health bloggers.