The federal government has received legal advice on making the same-sex marriage plebiscite result automatically trigger a change to the law.
But the government has refused an AAP request under freedom of information to release the legal advice from the office of the solicitor-general to Attorney-General George Brandis.
One of the possible compromises in trying to get the plebiscite bill through the Senate is to make it "self-executing".
This would mean if a majority 'yes' vote was achieved, the Marriage Act would be automatically changed without any further reference to the parliament.
Under the existing plan, if the plebiscite delivers a 'yes' result it would still require the lower and upper houses of parliament to pass a change to the Marriage Act.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Some coalition MPs have signalled they could vote against the Marriage Act change or abstain from voting.
AAP sought correspondence between the attorney-general's department and the solicitor-general's office relating to self-execution of the plebiscite.
Attorney-general's department acting assistant secretary Ashleigh Saint said she had decided all of the advice documents were "subject to legal professional privilege" and were therefore exempt from FOI.
"The legal advice was independent and confidential. I do not consider that the privilege ... has been waived," Ms Saint wrote.
