The Turnbull government will pass legislation before the plebiscite on same-sex marriage is held to guarantee that people know in advance exactly what they will be voting for.

If the plebiscite passes, the Marriage Act will be changed automatically to reflect the result.

Although Prime Minister Malcolm Turnbull has promised the Nationals and conservatives in his own ranks to adhere to Tony Abbott's timetable of a plebiscite after the next election, gay marriage advocates in the Liberal Party believe this initial legislation should be passed before the election to expedite the whole process afterwards.

Queensland Liberal MP Warren Entsch, who is discussing the matter with Mr Turnbull and Attorney-General George Brandis, told The Australian Financial Review on Wednesday that the legislation would set the time frame for the plebiscite. Andrew Meares

Queensland Liberal MP Warren Entsch, who is discussing the matter with Mr Turnbull and Attorney-General George Brandis, told The Australian Financial Review on Wednesday that the legislation would set the time frame for the plebiscite, which he argues should be much less than 100 days after the next federal election. Labor has promised a parliamentary vote within 100 days if it wins the election.

Change to be defined