Australian Prime Minister Tony Abbott has blocked his MPs from supporting legislation to legalise gay marriage.
After a six-hour meeting, Coalition members voted they will not have a free vote on the topic.
Liberal MP Andrew Laming says he was among a third of members who unsuccessfully opposed Mr Abbott.
"I was on the other side of that debate, strongly supporting a conscience vote, and I haven't been successful," said Mr Laming.
"Whatever might be chosen as a potential option for a future election term, that option remains definitely open and I'm very strongly in support of that as well."
Mr Abbott says of the 30 or so Liberal MPs who wanted a conscience vote, "half a dozen" would vote to keep the status quo anyway.
Mr Abbott has signalled a referendum or a conscience vote may be held on the same-sex marriage debate after the next election.
"I've come to the view, I believe this is the party room view, that this is the last term in which the Coalition party room can be bound, although we will definitely maintain the current position for the life of this term."
Mr Abbott's sister, who is engaged to a woman, said she was "very disappointed".
"For me it goes to core Liberal principles, which we are all equal before the law," she told news show Lateline.