He said the resourcing issues had caused lower staff morale because some officers were not getting a lunch break until nine hours into their 12-hour shift.
"The bulk of ambulance staff get pretty depressed and it makes it harder for you to be happy and give the best care when you are going from job to job and you're starving."
Northern Region general manager Greg Salmon said Auckland St John had been trialling the use of single-crew vehicles for lower priority calls. He said it was intended to keep ambulances free for life-threatening situations at no extra cost.
The initiative, which officially began in January this year, replaced four frontline ambulances with four single-crew vehicles during the day, and two ambulances with two single-crew vehicles during the night.
But signs of trouble emerged just a month into the initiative as patient demand increased and resources remained static, he said.
"It wasn't working as how we hoped," Salmon said. "What was happening too often was the cars were going [to patients] but we still had to call an ambulance and that put pressure on the frontline fleet. At the same time, our workload is increasing in Auckland." The St John annual report for 2011-12 shows single crew callouts were up on the previous year by more than 4000 incidents. One in nine emergency calls was attended by ambulance officers working alone - 43,791 out of the 387,472 calls, or 11.3 per cent.
Salmon said a significant increase in calls and a system failure forced dispatchers to send single-crew vehicles to jobs they could not handle.
"It is not the people, it is the system," he said.
"We should have funded the trial in addition [to ambulances]. But we believed the trial would be so successful it would compensate itself so if cars were doing their job as we hoped there would have been fewer jobs for ambulances to go to."
He said additional frontline ambulances have since been put on the road and discussions were underway with the Ministry of Health about demands and resources.