Prime Minister Bill English was rushed out a side entrance of Dunedin Hospital when protesters stormed an announcement of a $1 billion rebuild.

English was talking in the foyer with dignitaries who had gathered to hear the announcement of the new $1 billion plus hospital - the largest build of its type in New Zealand's history - when the protesters started chanting.

He was taken out a side door by security staff, while the 50-strong group of female protesters chanted for 'equal pay'.

HAMISH McNEILLY/STUFF Bill English at Dunedin Hospital on Friday morning.

Earlier English and Health Minister Jonathan Coleman confirmed the Government supported a single site hospital, with a preference at a central city site, with the rebuild potentially employ 1000 people.

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"This is the biggest hospital rebuild in the history of New Zealand," Coleman said.

HAMISH MCNEILLY/STUFF The visit by the Prime Minister was disrupted by protesters.

"It will be a fantastic facility."

The Government had been pushing for the facility earlier, and "there is no reason why we would sit on a completed business case for months and months and months . . . this is the earliest we could release it."

A decision was to go to Cabinet next year.

HAMISH McNEILLY/STUFF Jan Scott, 70, was misdiagnosed with inoperable lung cancer at Dunedin Hospital in June.

The new hospital, estimated to cost between $1.2bn and $1.4bn, will be the largest hospital rebuild in New Zealand history, Coleman claimed.

"We have been assessing the options around refurbishing the existing site and building a new hospital. The decision has been made to rebuild," he said.

"This would maximise the opportunity of having a purpose-built, state-of-the-art facility, while also minimising disruption to patients and staff."

"The original plan was to simply rebuild the services block, but the indicative business case has determined that the ward block also needs replacing and that has increased the cost significantly from the original $300 million estimate."

"The Ministry of Health is working to secure an appropriate site for the new hospital, with a strong preference for a central city location. Depending on the location the new hospital will be opened in 7 – 10 years."

Coleman announced the new project in Dunedin with Prime Minister Bill English on Saturday morning.

He said the Government would consider a private and public funding deal to build the hospital.