Mr Entsch will introduce a bill to legalise same-sex marriage into to the House of Representatives on Monday. He has acknowledged it is doomed for defeat after the Coalition party room on Tuesday decided against a conscience vote. Senator Dean Smith says he will note vote with his party on a same-sex marriage plebiscite. Credit:Alex Ellinghausen Mr Smith said on Wednesday: "In contemporary Australian society, it is no longer defensible for the state to deny proper and equal recognition of a marriage between two consenting adults, simply based on their sexuality. "I intend to use the full liberties available to me as a government backbench senator to support same sex marriage if a private member's bill comes before the Senate." Earlier on Wednesday, Prime Minister Tony Abbott said he would be disappointed if any of his backbenchers voted against party policy, but that they were entitled to vote according to their conscience. Cabinet members, on the other hand, would have to resign from the ministry if they voted in favour of same-sex marriage, he said.

Mr Smith said he had argued in Tuesday's marathon Coalition party room meeting that he believes all couples deserve the same legal rights. Dean Smith. Credit:Philip Gostelow "I also affirmed my strong view that given this issue is so heavily governed by a person's attitude to faith and sexuality, it is quite obvious that every parliamentarian should be able to vote according to their own conscience," he said. Mr Smith said Liberal politicians had been allowed to vote according to their conscience in at least three previous parliamentary debates on marriage and family law. These included the Marriage Bill in 1961 and the 1974 Marriage Law Bill regulating divorce, he said.

"I am disappointed there has been such a significant departure from the previous custom and practice of the Parliamentary Liberal Party," he said. Mr Smith said he supported Education Minister Christopher Pyne's view that the issue should have been debated in a separate meeting of the Liberal Party, without National Party members present. But he welcomed the commitment not to bind parliamentarians in future parliaments as a "clear and positive" outcome from the meeting and accepted many of his colleagues hold different views on the issue. Senator Smith revealed earlier this year that he had reversed his long-standing opposition to same-sex marriage. "It's getting harder and harder to justify opposing same-sex marriage in Australia," he said at the time. "Is this really the business of government in today's day and age? I'd argue no."

Mr Abbott said during Wednesday's question time that Mr Entsch's bill "will be treated the same way that all other private member's bills are treated in this chamber". "There will be no special treatment, no favouritism," he said. Leader of the house, Christopher Pyne confirmed on Wednesday that he had argued against having the Liberal and National parties discuss the issue together. "I'm of the view, and I was of the view yesterday, that the Liberal Party should have a meeting of its own to discuss this matter of whether there should be a free vote on the issue of marriage equality," Mr Pyne told Radio 2GB. He noted that he was not "talking about of school" because "that seems to have been splashed across everyone newspaper in Australia".

When asked if he had remembered that Mr Abbott had talked specifically of the Coalition discussing the issue before the 2013 election, Mr Pyne said no. "But I still felt ... [there is] absolutely no reason at all why the Liberal Party couldn't have met to discuss the issue itself." Mr Pyne stressed that half of the frontbench speakers at the marathon meeting were in favour of a free vote, while a third of the backbench backed a free vote. "But the decision was made not to have one." The Education Minister also suggested that he would now abide by the decision, as a cabinet minister.

"We have a party position on it, which as a member of the cabinet, obviously I am bound by." Follow us on Twitter