But the group argues that if existing civil celebrants are granted the right to refuse to conduct same-sex marriages, an "opt-out" system should apply and all newly registered celebrants should be required to conduct the ceremonies.

The proposals are contained in a submission to the Senate Select Committee examining the draft Marriage Amendment (Same-Sex Marriage) Bill put up for consultation by the federal Attorney-General.

The draft bill contains an exemption for civil celebrants.

It says that despite any law, civil celebrants may refuse to conduct same-sex ceremonies if their "conscientious or religious beliefs do not allow the marriage celebrant to solemnise the marriage".

The exemption would shield civil celebrants who refuse to conduct same-sex marriages from falling foul of anti-discrimination laws.

But in its submission to the committee, the NSW Parliamentary Working Group on Marriage Equality points out that by definition a civil celebrant performs marriages on behalf of the state, "thus providing a government service".

"The working group believes that there ought not to be any discrimination by celebrants in civil marriages under the state, regardless of the celebrant's personal, moral or religious beliefs," the submission says.

However, the group – comprised of Nationals MLC Trevor Khan, Labor MLC Penny Sharpe, Liberal MP Bruce Notley-Smith, Greens MP Jenny Leong and independent MP Alex Greenwich – also proposes a "middle-ground approach".

Should a blanket exemption be granted, the group proposes "opt-outs for currently registered marriage celebrants, while exclusively appointing as new marriage celebrants only those who will agree to marry same-sex couples".

The group's submission supports exemptions for religious ministers but argues the existing exemptions in the Marriage Act are adequate and do not require the specific inclusion of same-sex couples.

Brian Richardson, president of the Australian Federation of Civil Celebrants, said his organisation had yet to come to a formal position on the issue but expected to do so early next month.

Mr Richardson said the federation polled its 2000 members last year, asking the question, "do you support marriage equality?" Some 87 per cent of respondents said they do.

Mr Richardson said this indicated broad support among the membership for conducting same-sex marriage ceremonies.

"Probably our position would be that all celebrants should be treated equally," Mr Richardson said.

"If the legislation is to be enacted as drafted, we don't see that there would be a huge issue with celebrants wanting to opt out".