An Auckland Anglican priest has decided not to press charges against a woman who slashed a controversial billboard outside his church.

The hoarding outside St-Matthew-in-the-City showed Mary and Joseph in bed with a caption reading, "Poor Joseph, God was a hard act to follow."

On Friday night police arrested a woman for using a knife to slash the billboard, which the church took it down permanently on Saturday after three acts of vandalism.

Police said today the woman would not face prosecution because the church had decided it did not want to press charges.

Church vicar Archdeacon Glynn Cardy, who said the woman who attacked the billboard was a Christian fanatic, has now been invited to speak at a Melbourne progressive religion conference next year.

Archdeacon Cardy said his church was firmly on the progressive side of the Christian continuum and the billboard was about getting people to question what the Christmas conception story was all about.

"Is it about a spiritual male God sending down sperm so a child would be born, or is it about the power of love in our midst as seen in Jesus?" he said.

Common Dreams progressive religion conference president Richard Carter said delegates would want to hear more from Archdeacon Cardy when they convened in Melbourne next April.

"Whether you agree with the approach or not, this issue goes to the heart of progressive Christianity," Mr Carter said.

"It's about the shift in thinking from a set of supernatural beliefs, to how Jesus lived and encouraged others to live."

The billboard was attacked four times, including with paint and with a knife.

Archdeacon Cardy said he had no regrets about the billboard and the debate that it provoked.

"We are glad that discussion about Santa, food, and present-buying was momentarily usurped by a discussion about Jesus."

Close to 1000 delegates will attend the conference. They include renegade Canadian clergywoman Gretta Vosper, author of With or Without God: Why the Way We Live is More Important than What We Believe, and deposed Catholic priest Peter Kennedy, leader of the rebel St Mary's in Exile community in Brisbane.