The embattled city's most celebrated landmark building has been extensively damaged in the earthquakes over the last 18 months, with its spire snapping in half during the fatal 6.3-magnitude quake of February 22, 2011.
Ongoing shakes have caused further damage to the building, prompting today's decision, which confirms the worst fears for the Anglican congregation.
"The Anglican Diocese is facing a hard reality - the cathedral is the revered "Mother Church" but is not the only church in the diocese to have sustained damage, in some cases irreparable or too costly to repair," Bishop Victoria Matthews of the Anglican Diocese of Christchurch said.
She said it would be deconstructed with "the utmost care and respect" to a level of 2-3m for safety and to retrieve heritage items.
"There will be no bulldozers or wrecking balls on the job," she said.
The decision was a "courageous'' one according to Earthquake Recovery Minister Gerry Brownlee.
He said: "It's been a tough decision but I commend the courage of those who have had to come to this realisation today. I think they've reached a good decision, given the state of the building.
"We've got to remember that the Christ Church Cathedral does somewhat define the city, so it's a very,very sensitive building. The real challenge now is work out the shape of the building that defines us going forward.''
The 131-year-old cathedral withstood violent earthquakes in 1881, 1888, 1922, 1901 and even September 4, last year.
The New Zealand Historic Places Trust expressed its disappointment at the announcement, saying the building could have been restored or rebuilt in a recognisable form.
"The church's decision to deconstruct the cathedral down to sill level or a maximum of two to three metres around the full extent of the building will make it very difficult to retain any sense of this very important building as it once was,'' NZHPT chief executive Bruce Chapman said.
The trust had continued to provide heritage advice and engineering peer review of three options for the building that ranged from maximum retention to deconstruction to sill level of the entire building.
"The NZHPT would have preferred the option which sought maximum safe retention of the buildings heritage as a basis for rebuilding the Cathedral in a recognisable form.''
Mr Chapman said that while the trust appreciated that may be a more expensive option, restoration or reconstruction in a strengthened form remained a possibility, and there was an opportunity to explore options to obtain the necessary local, national and international financial support.
"As with many other heritage buildings, as well as its important primary role as a place of prayer and worship for the Anglican community, it is also a place symbolic of the identity of Christchurch. While the Cathedral is privately owned, management decisions need to be cognisant of the wide range of public values associated with the building,'' Mr Chapman said.
The retention of central city heritage landmarks such as the cathedral, the Roman Catholic Basilica, Arts Centre, Canterbury Provincial Chambers and Our City-O-Tautahi would enhance the wider economic recovery of the city and region through the redevelopment of cultural tourism in the CBD.
