The NSW government's decision to deny Sirius heritage protection has triggered mixed reactions.

The Environment and Heritage Minister Mark Speakman on Sunday announced Sirius would not be heritage protected, reaping the government around an extra $70 million to build new social housing.

Minister for Finance, Services and Property Dominic Perrottet said, "Divesting this site is going to fund hundreds more new social housing dwellings for those vulnerable members of our society who need them.

“Given the current waiting list for social housing, it's not fair for the Government to just sit on valuable assets when we can make better use of them to generate housing for those who need it most."

CBRE's Justin Brown, told the AFR the site could accommodate up to 220 apartments, which could fetch around $1.5 million to $2 million each.

The 79-apartment social housing block was designed in the 1970s, and has been considered controversial for its stark brutalist style

"Frankly, the Sirius building is not at all in harmony with the harbour and heritage that surrounds it," said Perrottet.

But artist Del Kathryn Barton told ABC Radio, "The demolition of the Sirius building would be a cultural tragedy. Around the world people are celebrating brutalist architecture. I'd like to think that Australia culture can have that cultural sophistication."

Shaun Carter, the NSW president of the Australian Institute of Architects and chairman of the Save Our Sirius Foundation, told the ABC, "It has social significance, it has cultural significance, it has environmental significance.

"Sirius not only has this architectural exemplary value but it also has social and cultural value — the history and the stories of the people of Sydney and how Sydney grew and changed."

The Urban Taskforce has welcomed the rejection of the heritage listing and is advocating for the replacement building to honour the history of the site.

“The current Sirius Building was very innovatory in its day,” said CEO Chris Johnson. “It is important that a replacement building is about the spirit of today while understanding its context.”

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