Moderate Liberal MPs are preparing to turn former prime minister Tony Abbott's words against him as they push to ditch the Coalition's policy of a plebiscite on same-sex marriage in favour of a conscience vote.

Following the Coalition's marathon party room debate on the issue in 2015, Mr Abbott said it would be the last term of Parliament in which MPs would have to vote against their conscience on same-sex marriage.

His comments at the late-night press conference, which followed six hours of heated debate, have not featured in the public discussion since then. But moderate MPs say they will use them as ammunition in any future party room debate on the issue.

Debate is set to flare up next month when Liberal senator Dean Smith introduces a private member's bill to legalise same-sex marriage.