The Anglican church revealed the move today at a press conference on the future of the Gothic-style building.
In a joint announcement with Canterbury Recovery Minister Gerry Brownlee, Bishop Victoria Matthews confirmed interim work will require controlled partial demolition and temporary measures to make the rest of the building safe.
This will allow key artefacts and heritage items to be removed, retained and stored until decisions about a future cathedral are made.
Bishop Matthews said: "The decision follows a challenging and complex assessment process including review and input by a range of involved and interested persons to identify options and risks, along with consideration of expert analysis and technical reports.
"At all times we have proceeded with a deep commitment to being faithful to the gospel we proclaim.''
The 120-year-old cathedral withstood violent earthquakes in 1881, 1888, 1922, 1901 and on September 4 last year.
But the 6.3-magnitude earthquake in February, which killed 182 people and reduced the cathedral's spire to rubble was followed by further significant damage on June 13.
The extent of the damage makes the building unpredictable and therefore unsafe.
Before the work is carried out, the bishop will have to deconsecrate the cathedral, meaning it becomes a secular, rather than sacred site.
Bishop Matthews said: "This has been a difficult decision for all involved as no one loves the cathedral as much as we do.
"However, this is the next step towards a decision about the future of the cathedral, which will combine the old and the new.''
She said it was "critically important'' to the bishop, dean and the Anglican community of Christchurch that the right decision is made about the church's base in the city in the short and long term.
There will be a public announcement once a decision is made on the future of each of the churches and facilities including the Christ Church Cathedral, and the location of the interim ministry.
The cathedral was consecrated on November 1, 1881.
It was designed by English Gothic designer George Gilbert Scott, but influential local architect Benjamin Mountfort supervised the work.
Although the building is based on traditional European cathedrals, it contains a number of New Zealand influences, including the use of matai and totara timber from Banks Peninsula, and stone came from local quarries.
Artwork on the walls express the Maori, Polynesian and European culture, with New Zealand flora and fauna depicted in stained glass and in carvings.
