A bill to legalise same-sex marriage would not force celebrants to marry gay couples if they didn't want to, its sponsor says.
But Conservative Party leader Colin Craig says the bill will not protect the rights of all celebrants who do not wish to marry same-sex couples.
A select committee last month recommended changing the bill to make it clear that no celebrant recognised by a religious body or nominated by an approved organisation would have to marry a couple if it meant contravening their own or the organisation's beliefs.
Critics say that would cover only about a third of celebrants and the rest, who are not linked to a religious organisation, will not be covered.
Mr Craig told TVNZ's Q+A programme today that the select committee had ignored advice to explicitly cover all celebrants.
"At the moment, the proposed amendment only protects 32 per cent of celebrants.
The other 68 you're hanging out to dry," he said.
Mr Craig called on the Government to guarantee the rights of all celebrants.
"Why not put that in law?"
Labour MP Louisa Wall, who sponsored the member's bill, disagreed that celebrants could be forced to marry same-sex couples against their will.
"The select committee was very clear, and I agree, that no celebrant ever should be forced. Why would you want a celebrant at a beautiful celebration actually not wanting to be there? It doesn't make any sense."
She said celebrants would be authorised but not obliged to carry out same-sex marriages.
"We've now made it really explicit that if you're an organisational celebrant - if you're a minister of religion - you explicitly now can say no, and be very clear about why you're doing that."
The bill also made it clear that churches could decline to carry out same-sex marriages in sacramental areas, but they could not discriminate when hiring out facilities.
"If a church currently hires out their hall for money, they can't discriminate against any group who chooses to hire out that hall," Ms Wall said.
Wellington barrister Graeme Edgeler said the bill would not force celebrants who were not linked to a religious organisation to carry out marriages.
But if an independent celebrant declined to marry a same-sex couple, the couple could then complain to the Human Rights Commission.
"It's not about [celebrants] being forced, it's about people getting in trouble afterwards if they didn't," he told APNZ.
"They're not breaking any rule in the Marriage Act, but rules in other acts. The main one would be the Human Rights Act, which says you can't discriminate on the basis on sexual orientation or gender."
A legal opinion from Auckland barrister Ian Bassett, prepared for conservative lobby group Family First, noted 32 per cent of celebrants were linked to religious organisations.
He said the bill would interfere with people's rights to act according to their beliefs and consciences.