Ambulance services will be cut without extra government funding, says the country's largest provider. St John warns it "cannot survive in the future" without more cash from taxpayers.

And ambulance providers have secured powerful support, with New Zealand First leader Winston Peters backing the funding boost - and promising to make it an election issue.

St John chief executive Peter Bradley says St John cannot continue providing the services it does now on the basis of charitable funding.

Cuts would include slower responses to non-urgent calls, reducing staff numbers by not replacing those who left, a reduction in training and fewer people answering calls from the public.

Intensive care paramedic Dean Brown told Mike Hosking it's an historic issue because St John was originally set up as a volunteer service.

"It's just never been brought into line with the other emergency services. It needs to be fixed, we can't continue the way it is."

He says paramedics provide a premium service on a "fish and chip budget".

"I believe these sort of things take time, but we are at that crisis point now, something has to change."