Liberal MPs are quietly lobbying to change the party's position on same-sex marriage to ensure a conscience vote on the issue, but are not pushing for a result before September's federal election.

MPs are privately raising concerns with Opposition Leader Tony Abbott about the Coalition's stance against same-sex marriage, but are aware that any major push to alter the party's position before the election could damage its campaign.

Pressure mounts for a conscience vote on same sex marriage. Credit:Dallas Kilponen

There is also a view that the party room is not yet ready to back a conscience vote and if MPs were forced to make a decision before September, it would lock in a status quo position.

But supporters are optimistic that post the election, the chances of the party room agreeing to a conscience vote would be boosted by new MPs in the parliament and growing support within Liberal ranks.