The Historic Places Trust wants demolition work on the ChristChurch Cathedral to be halted immediately.
The trust's board says it has engineering reports which suggest the cathedral can be retained in greater form than Anglican Church leaders believe.
Chairwoman Shonagh Kenderdine says the board respects the difficult decision made by the church to pull the cathedral down. However, it remains concerned about taking the most destructive option to make the cathedral safe.
The board wants deconstruction work to stop and is supporting the retention of as much of the cathedral's heritage fabric as possible.
Ms Kenderdine says time needs to be taken to find the money necessary to pursue the restoration option.
"ChristChurch Cathedral defines the city and province. It is a landmark that the whole community and visitors have an affinity with," she said.
The demolition of the cathedral began in March after it was deemed too badly damaged by the Christchurch earthquakes to be repaired.
The Anglican Church is planning to build a so-called cardboard cathedral a few blocks away in Latimer Square.
A group wanting the cathedral to be rebuilt protested outside an Anglican synod in the city over the weekend.