"Why has Maggie Barry, who is minister of both Conservation and Culture and Heritage, been silent about the threat to the Visitor Centre?"
The decision was "entirely consistent with the department's long neglect of the building", she said.
DOC said it had spent a "substantial" amount of money trying to maintain the centre. It estimated it would cost $3 million to fully restore.
John Scott's son, Jacob Scott, told Hawke's Bay Today the decision was "criminal". "The expose that will follow this will be unbelievable," he said.
The Haumoana artist said "settlement protocols" had muzzled Crown entities and the Wairoa District Council.
He said Ruapani, which has a claim on the lake, "now has another basis for compensation". "It's silliness because it's [the pending claim] actually going to cost a whole lot more than refurbishing this building.
"It's criminal really. The cost of refurbishment, which is disputed, is only a fraction of an Auckland house price."
President of Historic Places Aotearoa (HPA) James Blackburne also lamented the news.
"To be clear, the building is not earthquake prone and it will not cost millions of dollars to repair. There are also other parties interested in using the building. Is this the real reason that Thoe are wanting to have the building demolished?"
He said the late Bay architect's work was "of outstanding importance with respect to its architectural, cultural and heritage significance". A petition launched this week by HPA had attracted more than 750 signatures.
Conservation Minister Maggie Barry told Hawke's Bay Today she was confident the "correct process" had been followed. "I understand both DOC and Thoe have formed the strong view this is the best outcome for the future of the condemned building," Ms Barry said.
-To find out more about the petition, visit change.org