THE pastor at the centre of a debate with Kevin Rudd on same-sex marriage last night may not agree with the Prime Minister's view on the subject, but is glad he heard it.

"I had an idea he would respond like that because I've read some of his views before on the way he interprets the Bible," Brisbane's New Hope Church senior pastor Matt Prater said today.

"It was good to actually hear it and make him state his case clearly."

But the Prime Minister's response - including references to the New Testament - did little to change the preacher's opinion.

"It certainly won't change my view," he said.

"I have a pretty clear view of what I've read in the bible.

"I feel like I need to stick to my guns. Like (Opposition Leader) Tony Abbott is sticking to his guns, I'll stick to mine."

Kevin Rudd compares fight for gay marriage with slavery

KEVIN Rudd has given a passionate defence of same-sex marriage after being challenged by a Christian pastor on the ABC's Q & A show.

"People don't choose their sexuality, they are born that way,'' Mr Rudd said.

"The idea this is somehow an abnormal condition is wrong."

Pastor Matt Prater, who also works on Christian radio, said many people had phoned the station saying they would not be voting for Mr Rudd because he had chopped and changed his views on key issues, including marriage, to win votes.

Mr Rudd was asked why, as a Christian, he didn't "believe the words of Jesus in the Bible" on marriage being between a man and a woman.

"The Bible also says that slavery is a natural condition," Mr Rudd said, quoting the Apostle Paul.

Mr Rudd said he made his decision based on a good 'informed' Christian conscience', citing that the New Testament was all about love and tolerance.

He said the Bible was about "universal love, loving your fellow man".

Mr Rudd came out in support of gay marriage several months ago, while he was still in the political wilderness.

The move put pressure on the ALP to support marriage equality.

At the time, Mr Rudd said an encounter with a 'God-botherer' Pentecostal who is gay has helped changed his stance on gay marriage.

Mr Rudd said believed the church and state should have different positions on the question of same sex marriage.

While he said churches should not be forced to marry homosexuals, he believed gay people should have the right to be legally married.

Mr Rudd's put him firmly at odds with his Nambour sister Loree Rudd who quit the Australian Labor Party in November 2011 because of the party's decision during its national conference earlier this month to vote in favour of same-sex marriage.

Speaking on Q & A, Mr Rudd said homosexuality was not an abnormal condition and the Bible also said "slavery was a natural condition".

"If you accept it to be natural and normal to be gay then it follows it is not right for two folk who love each other to be denied marriage," he said.

His comments sparked a largely positive response on Twitter, though the LNP posted a video advertisement showing how often he had changed his views on issues.

Mr Rudd's wife Therese Rein tweeted: "You were bloody brilliant tonight Kevin. You in my opinion definitely deserve another term.''