Liberal MPs pushing for a free vote on same-sex marriage in Australia have stepped up their campaign, with a key moderate arguing the party has never denied its members a conscience vote granted to their Labor rivals.

Victoria MP Russell Broadbent said on Wednesday (14 December) the coalition should not be ‘afraid’ of a conscience vote on same-sex marriage while senator Simon Birmingham said he would continue to fight for a free vote.

Leader of the Opposition Tony Abbott this week declared there would be no conscience vote for the coalition following the Australian Labor Party national conference decision to do so.

Abbott originally said the partyroom would discuss the issue in February when the private member’s bill on same-sex marriage was introduced by Labor MP Stephen Jones.

But he now says the coalition would simply reaffirm the position it held prior to the last election, that marriage is between a man and a woman.

‘I think it's important that the Liberal Party honours its historical tradition of always granting its members greater freedom than does the Labor Party,’ Senator Birmingham told Sky News.

‘In this case, that would mean at least meeting the Labor Party on a conscience vote and I'll certainly take my viewpoint to the partyroom.’