A newborn child found on the doorstep of the Cathedral of St Paul was in good health and being cared for by local children's services officials.

Nathan Leonhardt, a custodian at the cathedral, discovered the child on January 4 as he was locking the building about 6pm following evening Mass. The baby was left in a plastic laundry basket between the exterior and interior doors of a church entrance.

Leonhardt and Fr John Ubel, cathedral rector, cared for the infant boy in the church sacristy until emergency responders arrived. The priest said he baptised the child while waiting for police and an ambulance to arrive.