“I have come to the conclusion that church and state can have different positions and practices on the question of same sex marriage,” Mr Rudd said. “I believe the secular Australian state should be able to recognise same sex marriage.”

Rudd talked about his discussion with a friend who is a gay Christian who asked him “had my views on same sex marriage changed?” He then goes on to fully explain his point of view, in the lengthy and thorough explanation.

“Some will ask why I am saying all this now. For me, this issue has been a difficult personal journey, as I have read much, and talked now with many people, and of late for the first time in a long time I have had the time to do both,” wrote Rudd in the blog.

“I have long resisted going with the growing tide of public opinion just for the sake of it. Those who know me well know that I have tried in good conscience to deal with the ethical fundamentals of the issue and reach an ethical conclusion.”

Rudd voted against legalising same sex marriage in September 2012 but now says he has changed his mind.

His annoucement comes as the UK Parliament wrestles with passing a bill on gay marriage, with the Conservative party divided on the issue.

New Zealand recently passed a bill to amend marriage rights for same sex couples, effectively legalising gay marriage.