Gay conversion therapy is "bigoted quackery" and it will be banned in Victoria, Premier Daniel Andrews has announced at a pride march in Melbourne.

The state government says the ban would be an Australian first and comes after an investigation by the Health Complaints Commission found the practice resulted in long-term psychological harm and distress.

AAP

The so-called therapy has changed and even cost people their lives, Mr Andrews said before joining the Midsumma Pride March in St Kilda on Sunday.

"This bigoted quackery that masquerades as healthcare, the notion that any gay Victorian is broken and needs to be fixed ... that's such a hurtful, wrong and frankly an absolutely disgraceful way to approach what should be about inclusion and acceptance and valuing people just for who they are," he said.

It'll be a year at least before legislation is introduced to parliament, allowing for consultation and to ensure the laws are exactly right, Equality Minister Martin Foley said.

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"The Health Complaints Commission's report points to some deep seated, well entrenched practices here," he said.

"We want to make sure we don't push those practices to the fringe of society and underground, so getting this right is actually quite the complex process."

The proposed legislation is expected to include a mix of civil and criminal laws and educative measures, to be determined through extensive and respectful consultation with communities including LGBTI people and faith-based organisations.