A small band of "rebel" Liberal MPs has shelved the option of crossing the floor to force a parliamentary debate on same-sex marriage this year after the party strongly re-affirmed its support for a plebiscite.

Liberal MPs on Monday overwhelmingly supported the Coalition's election commitment to hold a plebiscite - preferably through a compulsory vote at the ballot box or, if that is rejected by the Senate, through a voluntary postal plebiscite.

Four Liberal MPs - Warren Entsch, Tim Wilson, Trevor Evans and Trent Zimmerman - helped force Monday's party room meeting by leaving open the possibility of suspending standing orders in the House of Representatives to force a vote on same-sex marriage if they were denied a conscience vote.

Senator Dean Smith would then move their private member's bill in the Senate.