Tony Abbott has failed in his bid to effectively kill off legislation allowing same-sex couples to marry.
The former prime minister's amendment to the bill before parliament was shut down on Thursday, allowing it to proceed to the final stages of becoming law.
Veteran Liberal MP Warren Entsch told MPs that agreeing to Mr Abbott's proposed change would have stopped progress of the legislation which passed the Senate last week without amendment.
"I ask colleagues to remember that Australians have emphatically voted to end discrimination against the LGBTI community, their friends, family and colleagues," he said.
Mr Abbott said he moved the amendment "out of respect for the millions of Australians who take religious freedom seriously".
"Out of respect for the millions who want the SSM bill swiftly passed I chose not to divide on it," he tweeted.
Mr Entsch thanked the 125 MPs who spoke during more than 21.5 hours of debate on the bill, which he co-signed with gay Liberal senator Dean Smith and three others.
Among the highs and lows was colleague Tim Wilson's historic proposal to his partner Ryan on the floor of parliament.
But Mr Entsch made special mention of the contribution from crossbencher Bob Katter, the last MP to speak on Wednesday night.
"His pathetic attempts at humour, insensitivity and grossly misleading comments were devoid of any facts and were highly offensive, embarrassing and cringe-worthy," he said.
"They need to be called out for what they are. His speech exemplifies what the LGBTI community have had to endure for so long."
The bill is expected to reach a final vote later on Thursday, after parliament considers a series of amendments from conservative government MPs and the Greens.
It's unlikely any of the proposed changes will succeed.
© AAP 2017