Kate Forbes has said having children outside of marriage is "wrong"
The finance secretary, who is standing to replace Nicola Sturgeon as SNP leader, made the comments in an interview today.
"It's something that I would seek to avoid, for me personally, but it doesn't fuss me, or put me up or down, the choices that other people make," she told Sky News.
Asked if she thought it was right or wrong, she added: "In terms of my faith, my faith would say that sex is for marriage and that is the approach that I would practise."
Pressed on whether she thought it was wrong, Forbes continued: "For me, it would be wrong according to my faith, but for you I have no idea what your faith is. So, in a free society you can do what you want."
The MSP had earlier refused to quit the leadership race after facing a backlash for her opposition to same-sex marriage.
An SNP MP, who asked not to be named, told the Record: "I thought the intention was to select a First Minister to lead the country to a progressive future, not back to 1823".
Forbes, a committed member of the Free Church of Scotland, has already lost the support of several SNP MSPs and MPs who had supported her campaign for the party leadership.
Asked about the last 24 hours, Forbes said she thought it had brought to light a "fascinating question" at the heart of Scottish political discourse: "What does liberalism mean?"
"Have we become so illiberal that we cannot have these discussions or some people are beyond the pale?”, she told STV News.
"Because if some people are beyond the pale then those are dark and dangerous days for Scotland."
The Scottish Greens have also warned a power-sharing deal at Holyrood between the two parties would be "compromised" if Forbes became First Minister.
"We have a Bute House agreement. That's the cooperation agreement between the Greens and SNP," Ross Greer told Times Radio.
The MSP continued: "The Bute House agreement includes a commitment to see through the gender recognition reform bill that was passed overwhelmingly by the Scottish Parliament with yes votes from all five parties.
"So anybody who can't commit to seeing through these commitments, is compromising the Bute House agreement."
"Any candidate for First Minister, the Greens would need to see unequivocal support for LGBTQ rights, because we have more of that coming up on the parliamentary agenda this session, including a ban on so-called Conversion therapy that the Greens wrote into the programme for government."
Greer, who is also a committed Christian, said: "I respect other Christians who take a different point of view. But I absolutely hold to the idea that our state, the government, should treat everybody equally.
"I respect that other churches may disagree with my church. The Church of Scotland does conduct same sex marriages, the church that Kate Forbes is a member of does not. I respectfully disagree with that. But as respectfully, I object strongly to the idea that we should use government to prevent people entering into same sex marriage if they want to."
Finance secretary Forbes was believed to be an early frontrunner in the race to succeed Nicola Sturgeon as SNP leader and First Minister.
But the evangelical Christian’s comments on equal marriage have triggered a backlash amongst her allies.
Richard Lochhead, the just transition minister, indicated early support for her - but backtracked after the gay rights row.
He said: "I welcomed my colleague Kate Forbes’ decision to join the SNP leadership contest given her talents and felt it would give us a real contest - new ideas and a new approach that we desperately need.
"However, I agree we can’t have a Party Leader who’d vote against same sex marriage."
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