A warning by an ambulance service that it would stop sending sole paramedics to emergencies played a key role in the government's funding boost to ensure all ambulances are double crewed, according to St John's chief executive.
The government announced yesterday that almost $60 million had been set aside to ensure all ambulances had two staff by 2021.
But the paramedics' union and the country's only other ambulance operator said the funding fell short.
In 2015, St John's chief executive Peter Bradley wrote to the government saying single crewing was a significant clinical and staff safety risk.
He warned that from 2018 the service would no longer send an ambulance out with only one person in it.
He said the message triggered government action even though double crewing would not be fully in place under the new funding plan until 2021.
"Back in 2015 we were hoping that we would have heard about the outcome of this much sooner," he said.
"Here we are today 2017, we now have the annoucement and we'll get on and implement double crewing. It's a good step forward, it's taken longer than we would have liked, but at least we've now got a very positive outcome."
About 300 of the 430 new staff would be emergency medical assistants (EMAs) - a new role that requires just five months of training.
Lynette Blacklaws from First Union said because those people were not fully qualified paramedics, the ambulances could not really be described as double-crewed.
She said they were "assisted single crews" instead.
"It would cost the government about another $5.5 million to be able to have two qualified ambulance officers, rather than the assistants. So in the scheme of things, it's really a drop in the bucket," she said.
But Mr Bradley said the EMAs would be valuable.
"These more highly qualified people are currently working by themselves," he said. "They aren't there to supervise EMAs, EMAs are there to support the paramedic to provide fantastic and improved patient care. They're... someone who can drive the ambulance and have the paramedic in the back to provide care."
The country's only other ambulance service is Wellington Free.
Its chief executive Diana Crossan said double-crewing should have happened a long time ago and the funding boost did not go far enough because both services still relied on donations for about a quarter of their total funding.
"Our shortfall is about $6m and we go to the community for $4.2m in the last two years. And we work really hard to get it, because we need it. We need it for ordinary running of the ambulance."
"It seems strange to me that in 2017, New Zealand has a charity for its ambulance. For example, you wouldn't expect to shake a bucket to buy a police car," she said.
The Health Minister Jonathan Coleman said the government had no plans to fully fund either ambulance service.