Advocates for the restoration of the earthquake-damaged ChristChurch Cathedral say it could be repaired in a quarter of the time and at a third of the price the church's owners say.
The Great Christchurch Building Trust announced on Tuesday that independent engineers have put the cost at $67 million.
The Anglican Church has put the cost of restoring the stone cathedral at a maximum of $221 million and the longest building timeframe at 22 years.
Trust co-chair Jim Anderton said it would save $22 million the church has allowed for inflation by starting the job immediately.
Mr Anderton said the trust would cover the $6.8 million it is expected to cost to stabilise the building.
It is also prepared to help the church raise funds to meet the shortfall after the insurance payout is accounted for.
Mr Anderton said there is enormous goodwill world-wide for the cathedral to be restored and funding, as well as savings through pro-bono work, would be easily accessed.
Reverend Jayson Rhodes, a spokesperson for the Anglican Church, says some of the cost-cutting measures presented by the group are non-negotiable.
"At this stage they've only provided us with preliminary figures. Our advice from our engineers and from our quantity surveyors is any project must include elements including contingency, including escalation and the engineers are saying base isolation is essential."
He says the church received the pricing plan on Tuesday morning and is reviewing the documents.
The church has presented three options for the cathedral: restoring the building, replacing it with a timber building in a similar style, or using a different and more modern design.
The costings have been published on the Cathedral Conversations website for each part of the process of restoration or rebuilding.