If Parliament moves to make same-sex marriages legal, then "polygamous relationships need recognising as well", says the leader of the Conservative Party .



In a live discussion today, Labour MP Louisa Wall and Conservative Party leader Colin Craig went head to head on the issue of marriage equality.



Wall is leading the Marriage (Definition of Marriage) Amendment Bill, which has sparked heated debate since it was pulled from the ballot last week. Craig made headlines when the bill was drawn, after he said it wasn't "intelligent to pretend that homosexual relationships are normal".



During the live chat both sides aired a number of views, while fielding questions from readers.



In response to one question on whether the bill would just end up creating "fresh injustices" discriminating toward polygamy, Craig said the bill would inevitably raise that issue.



"Louisa and I agree that marriage just can't be open on the basis of people loving each other, it's a question of the right place to draw the line.



"If we are going to be consistent, and love is all that matters, then we will have to accept polygamous relationships need recognising as well," he said.



But Wall disagreed, saying marriage was based on love, which was why gay and lesbian people wanted the same rights.



"Marriage is the institution of two people who love each other committing themselves to a shared life together. This bill will not address polygamy or other forms of relationship."



Craig said he did not think New Zealand needed to change the existing law.



"I don't doubt there are many relationships that are genuinely loving but it doesn't mean they qualify to be defined as a marriage."



Craig also stood by his statement today that homosexual relationships were "not normal", saying he believed that was what a lot New Zealanders thought.



"I think this is what a lot of New Zealanders think, civil unions and subsequent changes to legislation (over 160 changes) created the level playing field that most New Zealanders are comfortable with.



"My statement is that it is not intelligent to pretend that a mum and dad as parents is the same as say two dads. I think the difference is important when we are talking about what is in the best interests of a child."



The most current figures suggest more than two-thirds of New Zealanders back a law change to allow same-sex couples to marry. At a recent debate hosted by Victoria University, gay Labour MP Charles Chauvel said about 63 per cent of the population supported the change, with more than 90 per cent of those backers coming from younger generations.



Wall said today there was definitely a "generational gap" between most of those who supported it, and most of those who didn't.