WHEN it comes to the issue of same-sex marriage Bathurst MP Paul Toole admits to having old-fashioned values.

This means he would not be prepared to support legislation to allow gay people to tie the knot.

His views on the controversial subject come as a bill that would allow same-sex couples in this state to wed is due to be introduced into the Upper House of NSW Parliament on Thursday.

The bill comes as a result of a group of Liberal, Nationals, Labor, Greens and independent MPs who have carefully crafted legislation that would allow same-sex couples to marry in NSW.

Expert legal opinion suggests that because it establishes "same-sex marriage" as distinct from the federal definition of "marriage" it can survive a High Court challenge.

But Mr Toole told the Western Advocate there was still a long, long way to go before the bill could become law.

"It's being introduced into the Upper House and no doubt there will be numerous speakers who want to have their say on it," he said.

"I think that will be a drawn out process and it could be early next year before it even gets to the Legislative Assembly (Lower House) for a vote. That's if it even gets that far at all.

"It's going to be tight, but it may stall in the Upper House and not go past there because of a lack of support."

Mr Toole said he believes there could be a lot of amendments to the bill along the way.

"So, who knows what it would end up being like if it did get to the Lower House," he said. "Because it's a conscience, MPs can vote with their heart and not be confined to party lines.

"Personally, I have always maintained the same position in regard to my opinion on same-sex marriage. I am old-fashioned and am against it."

Mr Toole's views on the subject are in stark contrast with Premier Barry O'Farrell who supports same-sex marriage.

"We agree to disagree with each other," he said.

"But there are some discussions around the NSW Parliament that this should not be a decision for us to make and it should be more of a federal issue."