Speakers addressing a crowd of up to 35,000 in Dunedin have slammed government misinformation and told MPs they will be responsible for deaths caused by a hospital downgrade.
A huge crowd has assembled in the Octagon after a noisy march through the central city from the dental school.
The Dunedin City Council estimated the turnout at up to 20,000 people.
"This will result in patient deaths. There's no if buts or maybes. It will just be a simple matter of time when that happens. I want it today to be very clear on whose shoulders the responsibility for that sits.
"The threat to the health of those of us here and our future loved ones is very real," she said.
"Our hospital community are shocked and disappointed at this week's news," Dr Sheila Barnett, a Dunedin anaesthetic doctor and clinical transformation group chair for the new hospital, told the crowd.
"Our team have worked for seven years balancing busy clinical jobs, providing common sense clinical input, and many of us have lived and breathed this project.
"There has been a lot of give and take, but the final design we had was balanced and it reflected what the southern region would need in the decades ahead. I know that what we have designed would have worked.
Anne Daniels (President of the New Zealand Nurses Organisation) challenged the government to produce evidence that the bill for the hopital could blow out to $3 billion.
"We are standing up against divide and rule based on this misinformation. We are told that other regional hospitals upgrades will miss out if Dunedin gets the hospital. Even the regions don't accept this. They were in Parliament saying, This is bulls***.
"We will fight until we get what we promised. We will not wait for justice to be done. The government has taken away from the people. It is time for us to take it back. Build it right."
The march, sparked by concern over cuts to the crucial project, has gained momentum since the government's shock announcement on Thursday that the project faces a significant downgrade.
She had voted for National in the last election and labelled Thursday's announcement "appalling".
James Moffat, of Caversham, said nurses at the hospital were not being treated fairly.
His sign said "pay our nurses properly now".
"Buildings don't cure people, people cure people," Mr Moffat said.
Joanna Inch, of Fairfield, attended the march with her 13-year-old daughter Ruby-Mae.
Ruby-Mae said it was not just elderly people who used the hospital, and younger people needed Healthcare to ensure they made it to 50.
"We need to make sure they do see that number"
John Howell, of North East Valley, said building the hospital was a matter of priorities.
The government was "completely full of s***" and was turning their back on it promise.
"They need to build this hospital, as originally promised".
Health Minister Shane Reti announced the main inpatient building could be drastically scaled back or dumped altogether in favour of retrofitting the old hospital.