Cabinet signed off on $1 billion for the Nelson Hospital redevelopment last year ahead of the election.
Boyack said she was yet to receive assurance from the new government as to whether it would fund the full amount.
"We are desperate for a new hospital, it is one of the worst buildings in the country, we've had that commitment from the previous Labour government and we need it from the new government.
"It's critical we get this new hospital building, it is critical that the funding is assured for it, and it is critical that it is done under the public system and not privatised."
The new coalition government has signalled it is open to privatising parts of the health system - something Boyack said had not worked for hospitals in the United Kingdom and in other parts of Europe.
She was worried the Nelson Hospital redevelopment could be used as a test-case when it comes to privatising health infrastructure.
"I'm very concerned that because Nelson is right at a critical phase in terms of the final design and enablement works - the project hasn't been put out for tender yet and it could be used as a guinea pig and that could be terrible for Nelson.
"We don't want to be tenants in our own health system."
Boyack said there were international examples of public-private partnerships leading to cost overruns, lower quality products and higher costs for the taxpayer.
Health Minister Dr Shane Reti said he was still awaiting officials' advice about the full portfolio of Health New Zealand's infrastructure projects - with a particular interest in large scale projects which were underway, or had recently been announced.
"What I am keen to initially understand is where these respective major infrastructure builds are at, on the spectrum of project phasing, and what funding commitments have been made to date."
The government would keep an open mind as it looked at the best way to deliver healthcare, he said.
