Western Australia will become the first state to apologise to women, children and families affected by its past adoption practices.

Health Minister Kim Hames said on Tuesday that Premier Colin Barnett would put forward a motion in parliament on October 19 that would enable him to make the apology.

The apology would be made on behalf of the state institutions that engaged in adopting out children under past governments, Dr Hames said in a statement.

He said "vulnerable" mothers may have not been given the opportunity to make informed decisions.
Dr Hames said from the 1940s to the 1980s, the legal, health and welfare systems of the day were unsupportive of pregnant unmarried women.

"I have spoken to mothers who were affected by these practices and have heard first-hand the impact that (it) has had on their lives," Dr Hames said.

"They have told me an apology will go some way to assisting to overcome what has, for some, been lifelong trauma."

Dr Hames said there were also plans to create a memorial.