Cr Russell Lund lodged a submission, backed by five other councillors, opposing changes which would reclassify Dunedin and coastal Otago from low-risk to a "medium seismic zone".
Under a low-risk classification, Dunedin’s heritage stock would benefit from upgrade opportunities without "seismic upgrade costs and the threat of demolition", Cr Lund said.
"The change to medium will hit Dunedin harder than any other centre in New Zealand due to its much higher concentration of heritage buildings, especially in the CBD."
The changes are part of the Building (Earthquake-prone Buildings) Amendment Bill, broadly intended to make seismic strengthening rules more pragmatic, less onerous and a better fit with earthquake risk.
Cr Lund said the Bill’s proposed classification of medium risk for Dunedin would likely require a "lesser scope" of work for heritage buildings, but at a much higher standard.
He said a scientific report used to justify the Bill relied on a series of assumptions with "no local evidence" and did not reach a consensus on its results.
Similarly, he said an accompanying economic analysis report included a "number [of] frankly stupid assessments untethered from reality and past experience".
The submission was co-signed by deputy mayor Cherry Lucas and councillors Andrew Simms, Lee Vandervis, Brent Weatherall and Benedict Ong, who Cr Lund approached for support.
He earlier criticised the Dunedin City Council for not submitting on the Bill but said he decided against taking a formal motion to council as he did not want to risk its failure.
"I wasn’t confident that the other councillors would support it without a great deal of amendment and argument," he said.
Last month a council spokesman said unless councillors directed otherwise, the council’s focus was on recent government announcements.
This included "major legislative proposals" announced pre-Christmas, such as local government and Resource Management Act reform.
Advocacy group Southern Heritage Trust also submitted on the Bill, supporting its intent but endorsing a low-risk rating for Dunedin.
Trustee Jo Galer said the city had "the most to lose", given its heritage status was a drawcard for visitors.
"It’s vital that any policy changes the government makes support this advantage that is more important to Dunedin than any other main centre," she said.
"As they are, these proposed changes are not equitable."
The government’s Transport and Infrastructure select committee will consider submissions — their report to the House is due on June 16.
