The conservative Anglican bishop of north-west WA is threatening to abandon registering marriages if the Yes vote prevails in the same-sex marriage survey and religious protections are weak.

Criticising the Federal Government’s handling of the postal survey, Bishop of North West Australia Gary Nelson said details of the legislation should have been released before the vote began.

He warned that if religious protections fell short, the diocese would have to withdraw from providing all marriage approvals.

“If we are in a situation where there isn’t enough religious exemptions regarding marrying same-sex people, then we’d have to pull out from being celebrants, so just withdraw all the approvals for everyone,” Bishop Nelson told The West Australian.

“Even if we withdrew licences and a same-sex couple came in saying, ‘We want to use your building’, and we say no, will we have a right to say no to a use of our building?

“All of those things are still unclear.”

There is a split between the Geraldton-based North West diocese and Anglican leaders in Perth, several of whom have publicly backed the Yes campaign.

Bishop Nelson said the northern diocese would not act on marriage approvals unless it had to but protections proposed in the past had been “barely adequate” and it remained unclear which would become law.

While there would probably be some protections in place for religious ministers, there was evidence overseas where gay marriage had been legalised of protections being “whittled away” and “conscientious objectors” being left exposed.

Prime Minister Malcolm Turnbull, who backs same-sex marriage, has said that if a Yes vote prevails, Parliament will debate the legislation and safeguards needed to protect religious freedoms.

A group of sceptical conservative MPs is understood to be preparing its own Bill to change the Marriage Act, including protection for religious freedoms and those who oppose same-sex marriage “beyond the ceremony”.