Exactly where Jesus came from will be fiercely debated in at least one part of Auckland this Christmas.

A billboard put outside St Matthew-in-the-City shows the Virgin Mary and Joseph in bed together. Joseph's looking dejected, as Mary's eyes are raised wistfully towards the heavens.

The slogan above them reads: "Poor Joseph. God was a hard act to follow."

Archdeacon Glynn Cardy says the image is designed to provoke thought and conversation about the true origins of Christmas. He says progressive Christianity is distinctive in that not only does it articulate a clear view, it is also interested in engaging with those who differ.

But the Catholic Church wants to know why the Anglican Church is questioning where Jesus came from.

Spokeswoman Lyndsay Freer says it is a distinctly non-Christian message. She says the Christian faith was founded on the belief that Jesus is the son of God and was not conceived through any human intervention.

She says she would be surprised if the billboard is representative of mainstream Anglican thinking.