Former Tony Abbott chief of staff Peta Credlin says it may be time to discuss a "Plan B" in relation to same-sex marriage.
Labor, the Greens and some crossbench senators say a proposed plebiscite on same-sex marriage is a waste of money and would divide the community and the change should be made via a parliamentary vote.
Ms Credlin said senior ministers had declined during the election campaign to talk about the prospect of the plebiscite-enabling bill not passing parliament, and Labor had yet to firm up its position.
"Now we are looking like there needs to be a discussion about Plan B," Ms Credlin told Sky News on Thursday.
She expected coalition MPs who had successfully sought the plebiscite when Mr Abbott was leader, but opposed the Marriage Act change, would support the will of the majority of voters.
"I think you will find in internal discussions as this machinery bill is developed ...that MPs on the coalition side, if they want the plebiscite, will have to learn to accept the terms of the peoples' vote at the end of it."
