Support for same-sex marriage has fallen ahead of a national survey on the issue, according to Newspoll.
The proportion of voters who support same-sex marriage now stands at 57 per cent, compared to 63 per cent in August and 62 per cent in September last year.
The no vote has lifted to 34 per cent, from 30 per cent in August and 32 per cent a year ago.
About nine per cent are uncommitted.
Newspoll, published in The Australian on Monday, collated its results from a survey of 1695 voters polled across the nation over four days from Thursday.
Support for same-sex marriage was highest amongst Labor and Greens voters, at 70 per cent and 85 per cent respectively.
But conservative voters are trailing, with coalition backers polling 47 per cent, alongside 35 per cent for One Nation supporters.
0:00 Prime Minister Malcolm Turnbull and Lucy Turnbull post their same sex marriage survey Share Prime Minister Malcolm Turnbull and Lucy Turnbull post their same sex marriage survey
Newspoll also found the federal coalition government is behind the Labor opposition in two-party preferred terms, at 46 per cent to 54 per cent.
Malcolm Turnbull has again lost ground to Bill Shorten as preferred prime minister and now sits on a 42 per cent approval rating against 31 per cent for the opposition leader, a four-point fall since the last poll.