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 with 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 among 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.

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.

Crossbench senator Derryn Hinch fears the same techniques of “divide and conquer” used in the republic debate are being tried again now.

“Sow some seeds of doubt in here, spread the issue so it’s just not yes or no on same sex marriage, it’s freedom of religion, it’s freedom of speech,” he told the Seven Network.

Senator Hinch, who says he’s stopped tweeting about the issue after posting off his ‘Yes’ vote, worries people are siding with ‘if in doubt don’t’.