The issue has come under the spotlight after seriously unwell elderly South Otago woman, Marlene Dormer, died in a single-crew ambulance. Her daughter believes Dormer would have survived had the paramedic been supported by an ambulance volunteer or firefighter.
St John - which receives about 70 per cent of its funding from the Health Ministry, Accident Compensation Corporation and district health boards - says it needs 350 extra staff costing $21m.
About 10 per cent of St John's emergency call-outs are attended by a single-crewed vehicle and in rural areas it rises to 21 per cent.
First Union says single crewing is dangerous and a serious problem in rural areas. "Without that second pair of hands, both the paramedic and the patient are put at risk," said union spokesman Neil Chapman.
A St John ambulance officer, who requested anonymity, said the dangers had been compounded by the requirement to use dashboard-mounted tablets or mobile data terminals (MDTs).
When driving alone to an incident at up to 130km/h, the distraction of having to read the tablet for information such as address corrections or advice that the scene is unsafe could cause an accident.
St John said the MDTs were considered best practice for emergency services, reduced response times and staff were expected to use them safely.